| File: | jdk/src/hotspot/share/runtime/objectMonitor.cpp |
| Warning: | line 1959, column 7 Value stored to 'prv' is never read |
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| 1 | /* |
| 2 | * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. |
| 8 | * |
| 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 12 | * version 2 for more details (a copy is included in the LICENSE file that |
| 13 | * accompanied this code). |
| 14 | * |
| 15 | * You should have received a copy of the GNU General Public License version |
| 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 18 | * |
| 19 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| 20 | * or visit www.oracle.com if you need additional information or have any |
| 21 | * questions. |
| 22 | * |
| 23 | */ |
| 24 | |
| 25 | #include "precompiled.hpp" |
| 26 | #include "classfile/vmSymbols.hpp" |
| 27 | #include "gc/shared/oopStorage.hpp" |
| 28 | #include "gc/shared/oopStorageSet.hpp" |
| 29 | #include "jfr/jfrEvents.hpp" |
| 30 | #include "jfr/support/jfrThreadId.hpp" |
| 31 | #include "logging/log.hpp" |
| 32 | #include "logging/logStream.hpp" |
| 33 | #include "memory/allocation.inline.hpp" |
| 34 | #include "memory/resourceArea.hpp" |
| 35 | #include "oops/markWord.hpp" |
| 36 | #include "oops/oop.inline.hpp" |
| 37 | #include "oops/oopHandle.inline.hpp" |
| 38 | #include "oops/weakHandle.inline.hpp" |
| 39 | #include "prims/jvmtiDeferredUpdates.hpp" |
| 40 | #include "prims/jvmtiExport.hpp" |
| 41 | #include "runtime/atomic.hpp" |
| 42 | #include "runtime/handles.inline.hpp" |
| 43 | #include "runtime/interfaceSupport.inline.hpp" |
| 44 | #include "runtime/mutexLocker.hpp" |
| 45 | #include "runtime/objectMonitor.hpp" |
| 46 | #include "runtime/objectMonitor.inline.hpp" |
| 47 | #include "runtime/orderAccess.hpp" |
| 48 | #include "runtime/osThread.hpp" |
| 49 | #include "runtime/perfData.hpp" |
| 50 | #include "runtime/safefetch.inline.hpp" |
| 51 | #include "runtime/safepointMechanism.inline.hpp" |
| 52 | #include "runtime/sharedRuntime.hpp" |
| 53 | #include "runtime/thread.inline.hpp" |
| 54 | #include "services/threadService.hpp" |
| 55 | #include "utilities/dtrace.hpp" |
| 56 | #include "utilities/macros.hpp" |
| 57 | #include "utilities/preserveException.hpp" |
| 58 | #if INCLUDE_JFR1 |
| 59 | #include "jfr/support/jfrFlush.hpp" |
| 60 | #endif |
| 61 | |
| 62 | #ifdef DTRACE_ENABLED |
| 63 | |
| 64 | // Only bother with this argument setup if dtrace is available |
| 65 | // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. |
| 66 | |
| 67 | |
| 68 | #define DTRACE_MONITOR_PROBE_COMMON(obj, thread) \ |
| 69 | char* bytes = NULL__null; \ |
| 70 | int len = 0; \ |
| 71 | jlong jtid = SharedRuntime::get_java_tid(thread); \ |
| 72 | Symbol* klassname = obj->klass()->name(); \ |
| 73 | if (klassname != NULL__null) { \ |
| 74 | bytes = (char*)klassname->bytes(); \ |
| 75 | len = klassname->utf8_length(); \ |
| 76 | } |
| 77 | |
| 78 | #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis){;} \ |
| 79 | { \ |
| 80 | if (DTraceMonitorProbes) { \ |
| 81 | DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 82 | HOTSPOT_MONITOR_WAIT(jtid, \ |
| 83 | (monitor), bytes, len, (millis)); \ |
| 84 | } \ |
| 85 | } |
| 86 | |
| 87 | #define HOTSPOT_MONITOR_contended__enter HOTSPOT_MONITOR_CONTENDED_ENTER |
| 88 | #define HOTSPOT_MONITOR_contended__entered HOTSPOT_MONITOR_CONTENDED_ENTERED |
| 89 | #define HOTSPOT_MONITOR_contended__exit HOTSPOT_MONITOR_CONTENDED_EXIT |
| 90 | #define HOTSPOT_MONITOR_notify HOTSPOT_MONITOR_NOTIFY |
| 91 | #define HOTSPOT_MONITOR_notifyAll HOTSPOT_MONITOR_NOTIFYALL |
| 92 | |
| 93 | #define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread){;} \ |
| 94 | { \ |
| 95 | if (DTraceMonitorProbes) { \ |
| 96 | DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 97 | HOTSPOT_MONITOR_##probe(jtid, \ |
| 98 | (uintptr_t)(monitor), bytes, len); \ |
| 99 | } \ |
| 100 | } |
| 101 | |
| 102 | #else // ndef DTRACE_ENABLED |
| 103 | |
| 104 | #define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon){;} {;} |
| 105 | #define DTRACE_MONITOR_PROBE(probe, obj, thread, mon){;} {;} |
| 106 | |
| 107 | #endif // ndef DTRACE_ENABLED |
| 108 | |
| 109 | // Tunables ... |
| 110 | // The knob* variables are effectively final. Once set they should |
| 111 | // never be modified hence. Consider using __read_mostly with GCC. |
| 112 | |
| 113 | int ObjectMonitor::Knob_SpinLimit = 5000; // derived by an external tool - |
| 114 | |
| 115 | static int Knob_Bonus = 100; // spin success bonus |
| 116 | static int Knob_BonusB = 100; // spin success bonus |
| 117 | static int Knob_Penalty = 200; // spin failure penalty |
| 118 | static int Knob_Poverty = 1000; |
| 119 | static int Knob_FixedSpin = 0; |
| 120 | static int Knob_PreSpin = 10; // 20-100 likely better |
| 121 | |
| 122 | DEBUG_ONLY(static volatile bool InitDone = false;)static volatile bool InitDone = false; |
| 123 | |
| 124 | OopStorage* ObjectMonitor::_oop_storage = NULL__null; |
| 125 | |
| 126 | // ----------------------------------------------------------------------------- |
| 127 | // Theory of operations -- Monitors lists, thread residency, etc: |
| 128 | // |
| 129 | // * A thread acquires ownership of a monitor by successfully |
| 130 | // CAS()ing the _owner field from null to non-null. |
| 131 | // |
| 132 | // * Invariant: A thread appears on at most one monitor list -- |
| 133 | // cxq, EntryList or WaitSet -- at any one time. |
| 134 | // |
| 135 | // * Contending threads "push" themselves onto the cxq with CAS |
| 136 | // and then spin/park. |
| 137 | // |
| 138 | // * After a contending thread eventually acquires the lock it must |
| 139 | // dequeue itself from either the EntryList or the cxq. |
| 140 | // |
| 141 | // * The exiting thread identifies and unparks an "heir presumptive" |
| 142 | // tentative successor thread on the EntryList. Critically, the |
| 143 | // exiting thread doesn't unlink the successor thread from the EntryList. |
| 144 | // After having been unparked, the wakee will recontend for ownership of |
| 145 | // the monitor. The successor (wakee) will either acquire the lock or |
| 146 | // re-park itself. |
| 147 | // |
| 148 | // Succession is provided for by a policy of competitive handoff. |
| 149 | // The exiting thread does _not_ grant or pass ownership to the |
| 150 | // successor thread. (This is also referred to as "handoff" succession"). |
| 151 | // Instead the exiting thread releases ownership and possibly wakes |
| 152 | // a successor, so the successor can (re)compete for ownership of the lock. |
| 153 | // If the EntryList is empty but the cxq is populated the exiting |
| 154 | // thread will drain the cxq into the EntryList. It does so by |
| 155 | // by detaching the cxq (installing null with CAS) and folding |
| 156 | // the threads from the cxq into the EntryList. The EntryList is |
| 157 | // doubly linked, while the cxq is singly linked because of the |
| 158 | // CAS-based "push" used to enqueue recently arrived threads (RATs). |
| 159 | // |
| 160 | // * Concurrency invariants: |
| 161 | // |
| 162 | // -- only the monitor owner may access or mutate the EntryList. |
| 163 | // The mutex property of the monitor itself protects the EntryList |
| 164 | // from concurrent interference. |
| 165 | // -- Only the monitor owner may detach the cxq. |
| 166 | // |
| 167 | // * The monitor entry list operations avoid locks, but strictly speaking |
| 168 | // they're not lock-free. Enter is lock-free, exit is not. |
| 169 | // For a description of 'Methods and apparatus providing non-blocking access |
| 170 | // to a resource,' see U.S. Pat. No. 7844973. |
| 171 | // |
| 172 | // * The cxq can have multiple concurrent "pushers" but only one concurrent |
| 173 | // detaching thread. This mechanism is immune from the ABA corruption. |
| 174 | // More precisely, the CAS-based "push" onto cxq is ABA-oblivious. |
| 175 | // |
| 176 | // * Taken together, the cxq and the EntryList constitute or form a |
| 177 | // single logical queue of threads stalled trying to acquire the lock. |
| 178 | // We use two distinct lists to improve the odds of a constant-time |
| 179 | // dequeue operation after acquisition (in the ::enter() epilogue) and |
| 180 | // to reduce heat on the list ends. (c.f. Michael Scott's "2Q" algorithm). |
| 181 | // A key desideratum is to minimize queue & monitor metadata manipulation |
| 182 | // that occurs while holding the monitor lock -- that is, we want to |
| 183 | // minimize monitor lock holds times. Note that even a small amount of |
| 184 | // fixed spinning will greatly reduce the # of enqueue-dequeue operations |
| 185 | // on EntryList|cxq. That is, spinning relieves contention on the "inner" |
| 186 | // locks and monitor metadata. |
| 187 | // |
| 188 | // Cxq points to the set of Recently Arrived Threads attempting entry. |
| 189 | // Because we push threads onto _cxq with CAS, the RATs must take the form of |
| 190 | // a singly-linked LIFO. We drain _cxq into EntryList at unlock-time when |
| 191 | // the unlocking thread notices that EntryList is null but _cxq is != null. |
| 192 | // |
| 193 | // The EntryList is ordered by the prevailing queue discipline and |
| 194 | // can be organized in any convenient fashion, such as a doubly-linked list or |
| 195 | // a circular doubly-linked list. Critically, we want insert and delete operations |
| 196 | // to operate in constant-time. If we need a priority queue then something akin |
| 197 | // to Solaris' sleepq would work nicely. Viz., |
| 198 | // http://agg.eng/ws/on10_nightly/source/usr/src/uts/common/os/sleepq.c. |
| 199 | // Queue discipline is enforced at ::exit() time, when the unlocking thread |
| 200 | // drains the cxq into the EntryList, and orders or reorders the threads on the |
| 201 | // EntryList accordingly. |
| 202 | // |
| 203 | // Barring "lock barging", this mechanism provides fair cyclic ordering, |
| 204 | // somewhat similar to an elevator-scan. |
| 205 | // |
| 206 | // * The monitor synchronization subsystem avoids the use of native |
| 207 | // synchronization primitives except for the narrow platform-specific |
| 208 | // park-unpark abstraction. See the comments in os_solaris.cpp regarding |
| 209 | // the semantics of park-unpark. Put another way, this monitor implementation |
| 210 | // depends only on atomic operations and park-unpark. The monitor subsystem |
| 211 | // manages all RUNNING->BLOCKED and BLOCKED->READY transitions while the |
| 212 | // underlying OS manages the READY<->RUN transitions. |
| 213 | // |
| 214 | // * Waiting threads reside on the WaitSet list -- wait() puts |
| 215 | // the caller onto the WaitSet. |
| 216 | // |
| 217 | // * notify() or notifyAll() simply transfers threads from the WaitSet to |
| 218 | // either the EntryList or cxq. Subsequent exit() operations will |
| 219 | // unpark the notifyee. Unparking a notifee in notify() is inefficient - |
| 220 | // it's likely the notifyee would simply impale itself on the lock held |
| 221 | // by the notifier. |
| 222 | // |
| 223 | // * An interesting alternative is to encode cxq as (List,LockByte) where |
| 224 | // the LockByte is 0 iff the monitor is owned. _owner is simply an auxiliary |
| 225 | // variable, like _recursions, in the scheme. The threads or Events that form |
| 226 | // the list would have to be aligned in 256-byte addresses. A thread would |
| 227 | // try to acquire the lock or enqueue itself with CAS, but exiting threads |
| 228 | // could use a 1-0 protocol and simply STB to set the LockByte to 0. |
| 229 | // Note that is is *not* word-tearing, but it does presume that full-word |
| 230 | // CAS operations are coherent with intermix with STB operations. That's true |
| 231 | // on most common processors. |
| 232 | // |
| 233 | // * See also http://blogs.sun.com/dave |
| 234 | |
| 235 | |
| 236 | void* ObjectMonitor::operator new (size_t size) throw() { |
| 237 | return AllocateHeap(size, mtInternal); |
| 238 | } |
| 239 | void* ObjectMonitor::operator new[] (size_t size) throw() { |
| 240 | return operator new (size); |
| 241 | } |
| 242 | void ObjectMonitor::operator delete(void* p) { |
| 243 | FreeHeap(p); |
| 244 | } |
| 245 | void ObjectMonitor::operator delete[] (void *p) { |
| 246 | operator delete(p); |
| 247 | } |
| 248 | |
| 249 | // Check that object() and set_object() are called from the right context: |
| 250 | static void check_object_context() { |
| 251 | #ifdef ASSERT1 |
| 252 | Thread* self = Thread::current(); |
| 253 | if (self->is_Java_thread()) { |
| 254 | // Mostly called from JavaThreads so sanity check the thread state. |
| 255 | JavaThread* jt = JavaThread::cast(self); |
| 256 | switch (jt->thread_state()) { |
| 257 | case _thread_in_vm: // the usual case |
| 258 | case _thread_in_Java: // during deopt |
| 259 | break; |
| 260 | default: |
| 261 | fatal("called from an unsafe thread state")do { (*g_assert_poison) = 'X';; report_fatal(INTERNAL_ERROR, "/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 261, "called from an unsafe thread state"); ::breakpoint(); } while (0); |
| 262 | } |
| 263 | assert(jt->is_active_Java_thread(), "must be active JavaThread")do { if (!(jt->is_active_Java_thread())) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 263, "assert(" "jt->is_active_Java_thread()" ") failed", "must be active JavaThread"); ::breakpoint(); } } while (0); |
| 264 | } else { |
| 265 | // However, ThreadService::get_current_contended_monitor() |
| 266 | // can call here via the VMThread so sanity check it. |
| 267 | assert(self->is_VM_thread(), "must be")do { if (!(self->is_VM_thread())) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 267, "assert(" "self->is_VM_thread()" ") failed", "must be" ); ::breakpoint(); } } while (0); |
| 268 | } |
| 269 | #endif // ASSERT |
| 270 | } |
| 271 | |
| 272 | ObjectMonitor::ObjectMonitor(oop object) : |
| 273 | _header(markWord::zero()), |
| 274 | _object(_oop_storage, object), |
| 275 | _owner(NULL__null), |
| 276 | _previous_owner_tid(0), |
| 277 | _next_om(NULL__null), |
| 278 | _recursions(0), |
| 279 | _EntryList(NULL__null), |
| 280 | _cxq(NULL__null), |
| 281 | _succ(NULL__null), |
| 282 | _Responsible(NULL__null), |
| 283 | _Spinner(0), |
| 284 | _SpinDuration(ObjectMonitor::Knob_SpinLimit), |
| 285 | _contentions(0), |
| 286 | _WaitSet(NULL__null), |
| 287 | _waiters(0), |
| 288 | _WaitSetLock(0) |
| 289 | { } |
| 290 | |
| 291 | ObjectMonitor::~ObjectMonitor() { |
| 292 | _object.release(_oop_storage); |
| 293 | } |
| 294 | |
| 295 | oop ObjectMonitor::object() const { |
| 296 | check_object_context(); |
| 297 | if (_object.is_null()) { |
| 298 | return NULL__null; |
| 299 | } |
| 300 | return _object.resolve(); |
| 301 | } |
| 302 | |
| 303 | oop ObjectMonitor::object_peek() const { |
| 304 | if (_object.is_null()) { |
| 305 | return NULL__null; |
| 306 | } |
| 307 | return _object.peek(); |
| 308 | } |
| 309 | |
| 310 | void ObjectMonitor::ExitOnSuspend::operator()(JavaThread* current) { |
| 311 | if (current->is_suspended()) { |
| 312 | _om->_recursions = 0; |
| 313 | _om->_succ = NULL__null; |
| 314 | // Don't need a full fence after clearing successor here because of the call to exit(). |
| 315 | _om->exit(current, false /* not_suspended */); |
| 316 | _om_exited = true; |
| 317 | |
| 318 | current->set_current_pending_monitor(_om); |
| 319 | } |
| 320 | } |
| 321 | |
| 322 | void ObjectMonitor::ClearSuccOnSuspend::operator()(JavaThread* current) { |
| 323 | if (current->is_suspended()) { |
| 324 | if (_om->_succ == current) { |
| 325 | _om->_succ = NULL__null; |
| 326 | OrderAccess::fence(); // always do a full fence when successor is cleared |
| 327 | } |
| 328 | } |
| 329 | } |
| 330 | |
| 331 | // ----------------------------------------------------------------------------- |
| 332 | // Enter support |
| 333 | |
| 334 | bool ObjectMonitor::enter(JavaThread* current) { |
| 335 | // The following code is ordered to check the most common cases first |
| 336 | // and to reduce RTS->RTO cache line upgrades on SPARC and IA32 processors. |
| 337 | |
| 338 | void* cur = try_set_owner_from(NULL__null, current); |
| 339 | if (cur == NULL__null) { |
| 340 | assert(_recursions == 0, "invariant")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 340, "assert(" "_recursions == 0" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 341 | return true; |
| 342 | } |
| 343 | |
| 344 | if (cur == current) { |
| 345 | // TODO-FIXME: check for integer overflow! BUGID 6557169. |
| 346 | _recursions++; |
| 347 | return true; |
| 348 | } |
| 349 | |
| 350 | if (current->is_lock_owned((address)cur)) { |
| 351 | assert(_recursions == 0, "internal state error")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 351, "assert(" "_recursions == 0" ") failed", "internal state error" ); ::breakpoint(); } } while (0); |
| 352 | _recursions = 1; |
| 353 | set_owner_from_BasicLock(cur, current); // Convert from BasicLock* to Thread*. |
| 354 | return true; |
| 355 | } |
| 356 | |
| 357 | // We've encountered genuine contention. |
| 358 | assert(current->_Stalled == 0, "invariant")do { if (!(current->_Stalled == 0)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 358, "assert(" "current->_Stalled == 0" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 359 | current->_Stalled = intptr_t(this); |
| 360 | |
| 361 | // Try one round of spinning *before* enqueueing current |
| 362 | // and before going through the awkward and expensive state |
| 363 | // transitions. The following spin is strictly optional ... |
| 364 | // Note that if we acquire the monitor from an initial spin |
| 365 | // we forgo posting JVMTI events and firing DTRACE probes. |
| 366 | if (TrySpin(current) > 0) { |
| 367 | assert(owner_raw() == current, "must be current: owner=" INTPTR_FORMAT, p2i(owner_raw()))do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 367, "assert(" "owner_raw() == current" ") failed", "must be current: owner=" "0x%016" "l" "x", p2i(owner_raw())); ::breakpoint(); } } while (0); |
| 368 | assert(_recursions == 0, "must be 0: recursions=" INTX_FORMAT, _recursions)do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 368, "assert(" "_recursions == 0" ") failed", "must be 0: recursions=" "%" "l" "d", _recursions); ::breakpoint(); } } while (0); |
| 369 | assert(object()->mark() == markWord::encode(this),do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 372, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "object mark must match encoded this: mark=" "0x%016" "l" "x" ", encoded this=" "0x%016" "l" "x", object()->mark ().value(), markWord::encode(this).value()); ::breakpoint(); } } while (0) |
| 370 | "object mark must match encoded this: mark=" INTPTR_FORMATdo { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 372, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "object mark must match encoded this: mark=" "0x%016" "l" "x" ", encoded this=" "0x%016" "l" "x", object()->mark ().value(), markWord::encode(this).value()); ::breakpoint(); } } while (0) |
| 371 | ", encoded this=" INTPTR_FORMAT, object()->mark().value(),do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 372, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "object mark must match encoded this: mark=" "0x%016" "l" "x" ", encoded this=" "0x%016" "l" "x", object()->mark ().value(), markWord::encode(this).value()); ::breakpoint(); } } while (0) |
| 372 | markWord::encode(this).value())do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 372, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "object mark must match encoded this: mark=" "0x%016" "l" "x" ", encoded this=" "0x%016" "l" "x", object()->mark ().value(), markWord::encode(this).value()); ::breakpoint(); } } while (0); |
| 373 | current->_Stalled = 0; |
| 374 | return true; |
| 375 | } |
| 376 | |
| 377 | assert(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 377, "assert(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 378 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 378, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 379 | assert(!SafepointSynchronize::is_at_safepoint(), "invariant")do { if (!(!SafepointSynchronize::is_at_safepoint())) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 379, "assert(" "!SafepointSynchronize::is_at_safepoint()" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 380 | assert(current->thread_state() != _thread_blocked, "invariant")do { if (!(current->thread_state() != _thread_blocked)) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 380, "assert(" "current->thread_state() != _thread_blocked" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 381 | |
| 382 | // Keep track of contention for JVM/TI and M&M queries. |
| 383 | add_to_contentions(1); |
| 384 | if (is_being_async_deflated()) { |
| 385 | // Async deflation is in progress and our contentions increment |
| 386 | // above lost the race to async deflation. Undo the work and |
| 387 | // force the caller to retry. |
| 388 | const oop l_object = object(); |
| 389 | if (l_object != NULL__null) { |
| 390 | // Attempt to restore the header/dmw to the object's header so that |
| 391 | // we only retry once if the deflater thread happens to be slow. |
| 392 | install_displaced_markword_in_object(l_object); |
| 393 | } |
| 394 | current->_Stalled = 0; |
| 395 | add_to_contentions(-1); |
| 396 | return false; |
| 397 | } |
| 398 | |
| 399 | JFR_ONLY(JfrConditionalFlushWithStacktrace<EventJavaMonitorEnter> flush(current);)JfrConditionalFlushWithStacktrace<EventJavaMonitorEnter> flush(current); |
| 400 | EventJavaMonitorEnter event; |
| 401 | if (event.is_started()) { |
| 402 | event.set_monitorClass(object()->klass()); |
| 403 | // Set an address that is 'unique enough', such that events close in |
| 404 | // time and with the same address are likely (but not guaranteed) to |
| 405 | // belong to the same object. |
| 406 | event.set_address((uintptr_t)this); |
| 407 | } |
| 408 | |
| 409 | { // Change java thread status to indicate blocked on monitor enter. |
| 410 | JavaThreadBlockedOnMonitorEnterState jtbmes(current, this); |
| 411 | |
| 412 | assert(current->current_pending_monitor() == NULL, "invariant")do { if (!(current->current_pending_monitor() == __null)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 412, "assert(" "current->current_pending_monitor() == __null" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 413 | current->set_current_pending_monitor(this); |
| 414 | |
| 415 | DTRACE_MONITOR_PROBE(contended__enter, this, object(), current){;}; |
| 416 | if (JvmtiExport::should_post_monitor_contended_enter()) { |
| 417 | JvmtiExport::post_monitor_contended_enter(current, this); |
| 418 | |
| 419 | // The current thread does not yet own the monitor and does not |
| 420 | // yet appear on any queues that would get it made the successor. |
| 421 | // This means that the JVMTI_EVENT_MONITOR_CONTENDED_ENTER event |
| 422 | // handler cannot accidentally consume an unpark() meant for the |
| 423 | // ParkEvent associated with this ObjectMonitor. |
| 424 | } |
| 425 | |
| 426 | OSThreadContendState osts(current->osthread()); |
| 427 | |
| 428 | assert(current->thread_state() == _thread_in_vm, "invariant")do { if (!(current->thread_state() == _thread_in_vm)) { (* g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 428, "assert(" "current->thread_state() == _thread_in_vm" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 429 | |
| 430 | for (;;) { |
| 431 | ExitOnSuspend eos(this); |
| 432 | { |
| 433 | ThreadBlockInVMPreprocess<ExitOnSuspend> tbivs(current, eos, true /* allow_suspend */); |
| 434 | EnterI(current); |
| 435 | current->set_current_pending_monitor(NULL__null); |
| 436 | // We can go to a safepoint at the end of this block. If we |
| 437 | // do a thread dump during that safepoint, then this thread will show |
| 438 | // as having "-locked" the monitor, but the OS and java.lang.Thread |
| 439 | // states will still report that the thread is blocked trying to |
| 440 | // acquire it. |
| 441 | // If there is a suspend request, ExitOnSuspend will exit the OM |
| 442 | // and set the OM as pending. |
| 443 | } |
| 444 | if (!eos.exited()) { |
| 445 | // ExitOnSuspend did not exit the OM |
| 446 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 446, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 447 | break; |
| 448 | } |
| 449 | } |
| 450 | |
| 451 | // We've just gotten past the enter-check-for-suspend dance and we now own |
| 452 | // the monitor free and clear. |
| 453 | } |
| 454 | |
| 455 | add_to_contentions(-1); |
| 456 | assert(contentions() >= 0, "must not be negative: contentions=%d", contentions())do { if (!(contentions() >= 0)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 456, "assert(" "contentions() >= 0" ") failed", "must not be negative: contentions=%d" , contentions()); ::breakpoint(); } } while (0); |
| 457 | current->_Stalled = 0; |
| 458 | |
| 459 | // Must either set _recursions = 0 or ASSERT _recursions == 0. |
| 460 | assert(_recursions == 0, "invariant")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 460, "assert(" "_recursions == 0" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 461 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 461, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 462 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 462, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 463 | assert(object()->mark() == markWord::encode(this), "invariant")do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 463, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 464 | |
| 465 | // The thread -- now the owner -- is back in vm mode. |
| 466 | // Report the glorious news via TI,DTrace and jvmstat. |
| 467 | // The probe effect is non-trivial. All the reportage occurs |
| 468 | // while we hold the monitor, increasing the length of the critical |
| 469 | // section. Amdahl's parallel speedup law comes vividly into play. |
| 470 | // |
| 471 | // Another option might be to aggregate the events (thread local or |
| 472 | // per-monitor aggregation) and defer reporting until a more opportune |
| 473 | // time -- such as next time some thread encounters contention but has |
| 474 | // yet to acquire the lock. While spinning that thread could |
| 475 | // spinning we could increment JVMStat counters, etc. |
| 476 | |
| 477 | DTRACE_MONITOR_PROBE(contended__entered, this, object(), current){;}; |
| 478 | if (JvmtiExport::should_post_monitor_contended_entered()) { |
| 479 | JvmtiExport::post_monitor_contended_entered(current, this); |
| 480 | |
| 481 | // The current thread already owns the monitor and is not going to |
| 482 | // call park() for the remainder of the monitor enter protocol. So |
| 483 | // it doesn't matter if the JVMTI_EVENT_MONITOR_CONTENDED_ENTERED |
| 484 | // event handler consumed an unpark() issued by the thread that |
| 485 | // just exited the monitor. |
| 486 | } |
| 487 | if (event.should_commit()) { |
| 488 | event.set_previousOwner(_previous_owner_tid); |
| 489 | event.commit(); |
| 490 | } |
| 491 | OM_PERFDATA_OP(ContendedLockAttempts, inc())do { if (ObjectMonitor::_sync_ContendedLockAttempts != __null && PerfDataManager::has_PerfData()) { ObjectMonitor:: _sync_ContendedLockAttempts->inc(); } } while (0); |
| 492 | return true; |
| 493 | } |
| 494 | |
| 495 | // Caveat: TryLock() is not necessarily serializing if it returns failure. |
| 496 | // Callers must compensate as needed. |
| 497 | |
| 498 | int ObjectMonitor::TryLock(JavaThread* current) { |
| 499 | void* own = owner_raw(); |
| 500 | if (own != NULL__null) return 0; |
| 501 | if (try_set_owner_from(NULL__null, current) == NULL__null) { |
| 502 | assert(_recursions == 0, "invariant")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 502, "assert(" "_recursions == 0" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 503 | return 1; |
| 504 | } |
| 505 | // The lock had been free momentarily, but we lost the race to the lock. |
| 506 | // Interference -- the CAS failed. |
| 507 | // We can either return -1 or retry. |
| 508 | // Retry doesn't make as much sense because the lock was just acquired. |
| 509 | return -1; |
| 510 | } |
| 511 | |
| 512 | // Deflate the specified ObjectMonitor if not in-use. Returns true if it |
| 513 | // was deflated and false otherwise. |
| 514 | // |
| 515 | // The async deflation protocol sets owner to DEFLATER_MARKER and |
| 516 | // makes contentions negative as signals to contending threads that |
| 517 | // an async deflation is in progress. There are a number of checks |
| 518 | // as part of the protocol to make sure that the calling thread has |
| 519 | // not lost the race to a contending thread. |
| 520 | // |
| 521 | // The ObjectMonitor has been successfully async deflated when: |
| 522 | // (contentions < 0) |
| 523 | // Contending threads that see that condition know to retry their operation. |
| 524 | // |
| 525 | bool ObjectMonitor::deflate_monitor() { |
| 526 | if (is_busy()) { |
| 527 | // Easy checks are first - the ObjectMonitor is busy so no deflation. |
| 528 | return false; |
| 529 | } |
| 530 | |
| 531 | if (ObjectSynchronizer::is_final_audit() && owner_is_DEFLATER_MARKER()) { |
| 532 | // The final audit can see an already deflated ObjectMonitor on the |
| 533 | // in-use list because MonitorList::unlink_deflated() might have |
| 534 | // blocked for the final safepoint before unlinking all the deflated |
| 535 | // monitors. |
| 536 | assert(contentions() < 0, "must be negative: contentions=%d", contentions())do { if (!(contentions() < 0)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 536, "assert(" "contentions() < 0" ") failed", "must be negative: contentions=%d" , contentions()); ::breakpoint(); } } while (0); |
| 537 | // Already returned 'true' when it was originally deflated. |
| 538 | return false; |
| 539 | } |
| 540 | |
| 541 | const oop obj = object_peek(); |
| 542 | |
| 543 | if (obj == NULL__null) { |
| 544 | // If the object died, we can recycle the monitor without racing with |
| 545 | // Java threads. The GC already broke the association with the object. |
| 546 | set_owner_from(NULL__null, DEFLATER_MARKERreinterpret_cast<void*>(-1)); |
| 547 | assert(contentions() >= 0, "must be non-negative: contentions=%d", contentions())do { if (!(contentions() >= 0)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 547, "assert(" "contentions() >= 0" ") failed", "must be non-negative: contentions=%d" , contentions()); ::breakpoint(); } } while (0); |
| 548 | _contentions = INT_MIN(-2147483647 -1); // minimum negative int |
| 549 | } else { |
| 550 | // Attempt async deflation protocol. |
| 551 | |
| 552 | // Set a NULL owner to DEFLATER_MARKER to force any contending thread |
| 553 | // through the slow path. This is just the first part of the async |
| 554 | // deflation dance. |
| 555 | if (try_set_owner_from(NULL__null, DEFLATER_MARKERreinterpret_cast<void*>(-1)) != NULL__null) { |
| 556 | // The owner field is no longer NULL so we lost the race since the |
| 557 | // ObjectMonitor is now busy. |
| 558 | return false; |
| 559 | } |
| 560 | |
| 561 | if (contentions() > 0 || _waiters != 0) { |
| 562 | // Another thread has raced to enter the ObjectMonitor after |
| 563 | // is_busy() above or has already entered and waited on |
| 564 | // it which makes it busy so no deflation. Restore owner to |
| 565 | // NULL if it is still DEFLATER_MARKER. |
| 566 | if (try_set_owner_from(DEFLATER_MARKERreinterpret_cast<void*>(-1), NULL__null) != DEFLATER_MARKERreinterpret_cast<void*>(-1)) { |
| 567 | // Deferred decrement for the JT EnterI() that cancelled the async deflation. |
| 568 | add_to_contentions(-1); |
| 569 | } |
| 570 | return false; |
| 571 | } |
| 572 | |
| 573 | // Make a zero contentions field negative to force any contending threads |
| 574 | // to retry. This is the second part of the async deflation dance. |
| 575 | if (Atomic::cmpxchg(&_contentions, 0, INT_MIN(-2147483647 -1)) != 0) { |
| 576 | // Contentions was no longer 0 so we lost the race since the |
| 577 | // ObjectMonitor is now busy. Restore owner to NULL if it is |
| 578 | // still DEFLATER_MARKER: |
| 579 | if (try_set_owner_from(DEFLATER_MARKERreinterpret_cast<void*>(-1), NULL__null) != DEFLATER_MARKERreinterpret_cast<void*>(-1)) { |
| 580 | // Deferred decrement for the JT EnterI() that cancelled the async deflation. |
| 581 | add_to_contentions(-1); |
| 582 | } |
| 583 | return false; |
| 584 | } |
| 585 | } |
| 586 | |
| 587 | // Sanity checks for the races: |
| 588 | guarantee(owner_is_DEFLATER_MARKER(), "must be deflater marker")do { if (!(owner_is_DEFLATER_MARKER())) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 588, "guarantee(" "owner_is_DEFLATER_MARKER()" ") failed", "must be deflater marker" ); ::breakpoint(); } } while (0); |
| 589 | guarantee(contentions() < 0, "must be negative: contentions=%d",do { if (!(contentions() < 0)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 590, "guarantee(" "contentions() < 0" ") failed", "must be negative: contentions=%d" , contentions()); ::breakpoint(); } } while (0) |
| 590 | contentions())do { if (!(contentions() < 0)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 590, "guarantee(" "contentions() < 0" ") failed", "must be negative: contentions=%d" , contentions()); ::breakpoint(); } } while (0); |
| 591 | guarantee(_waiters == 0, "must be 0: waiters=%d", _waiters)do { if (!(_waiters == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 591, "guarantee(" "_waiters == 0" ") failed", "must be 0: waiters=%d" , _waiters); ::breakpoint(); } } while (0); |
| 592 | guarantee(_cxq == NULL, "must be no contending threads: cxq="do { if (!(_cxq == __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 593, "guarantee(" "_cxq == NULL" ") failed", "must be no contending threads: cxq=" "0x%016" "l" "x", p2i(_cxq)); ::breakpoint(); } } while (0) |
| 593 | INTPTR_FORMAT, p2i(_cxq))do { if (!(_cxq == __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 593, "guarantee(" "_cxq == NULL" ") failed", "must be no contending threads: cxq=" "0x%016" "l" "x", p2i(_cxq)); ::breakpoint(); } } while (0); |
| 594 | guarantee(_EntryList == NULL,do { if (!(_EntryList == __null)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 596, "guarantee(" "_EntryList == NULL" ") failed", "must be no entering threads: EntryList=" "0x%016" "l" "x", p2i(_EntryList)); ::breakpoint(); } } while (0) |
| 595 | "must be no entering threads: EntryList=" INTPTR_FORMAT,do { if (!(_EntryList == __null)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 596, "guarantee(" "_EntryList == NULL" ") failed", "must be no entering threads: EntryList=" "0x%016" "l" "x", p2i(_EntryList)); ::breakpoint(); } } while (0) |
| 596 | p2i(_EntryList))do { if (!(_EntryList == __null)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 596, "guarantee(" "_EntryList == NULL" ") failed", "must be no entering threads: EntryList=" "0x%016" "l" "x", p2i(_EntryList)); ::breakpoint(); } } while (0); |
| 597 | |
| 598 | if (obj != NULL__null) { |
| 599 | if (log_is_enabled(Trace, monitorinflation)(LogImpl<(LogTag::_monitorinflation), (LogTag::__NO_TAG), ( LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag ::__NO_TAG)>::is_level(LogLevel::Trace))) { |
| 600 | ResourceMark rm; |
| 601 | log_trace(monitorinflation)(!(LogImpl<(LogTag::_monitorinflation), (LogTag::__NO_TAG) , (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG)>::is_level(LogLevel::Trace))) ? (void) 0 : LogImpl<(LogTag::_monitorinflation), (LogTag::__NO_TAG ), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG) , (LogTag::__NO_TAG)>::write<LogLevel::Trace>("deflate_monitor: object=" INTPTR_FORMAT"0x%016" "l" "x" |
| 602 | ", mark=" INTPTR_FORMAT"0x%016" "l" "x" ", type='%s'", |
| 603 | p2i(obj), obj->mark().value(), |
| 604 | obj->klass()->external_name()); |
| 605 | } |
| 606 | |
| 607 | // Install the old mark word if nobody else has already done it. |
| 608 | install_displaced_markword_in_object(obj); |
| 609 | } |
| 610 | |
| 611 | // We leave owner == DEFLATER_MARKER and contentions < 0 |
| 612 | // to force any racing threads to retry. |
| 613 | return true; // Success, ObjectMonitor has been deflated. |
| 614 | } |
| 615 | |
| 616 | // Install the displaced mark word (dmw) of a deflating ObjectMonitor |
| 617 | // into the header of the object associated with the monitor. This |
| 618 | // idempotent method is called by a thread that is deflating a |
| 619 | // monitor and by other threads that have detected a race with the |
| 620 | // deflation process. |
| 621 | void ObjectMonitor::install_displaced_markword_in_object(const oop obj) { |
| 622 | // This function must only be called when (owner == DEFLATER_MARKER |
| 623 | // && contentions <= 0), but we can't guarantee that here because |
| 624 | // those values could change when the ObjectMonitor gets moved from |
| 625 | // the global free list to a per-thread free list. |
| 626 | |
| 627 | guarantee(obj != NULL, "must be non-NULL")do { if (!(obj != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 627, "guarantee(" "obj != NULL" ") failed", "must be non-NULL" ); ::breakpoint(); } } while (0); |
| 628 | |
| 629 | // Separate loads in is_being_async_deflated(), which is almost always |
| 630 | // called before this function, from the load of dmw/header below. |
| 631 | |
| 632 | // _contentions and dmw/header may get written by different threads. |
| 633 | // Make sure to observe them in the same order when having several observers. |
| 634 | OrderAccess::loadload_for_IRIW(); |
| 635 | |
| 636 | const oop l_object = object_peek(); |
| 637 | if (l_object == NULL__null) { |
| 638 | // ObjectMonitor's object ref has already been cleared by async |
| 639 | // deflation or GC so we're done here. |
| 640 | return; |
| 641 | } |
| 642 | assert(l_object == obj, "object=" INTPTR_FORMAT " must equal obj="do { if (!(l_object == obj)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 643, "assert(" "l_object == obj" ") failed", "object=" "0x%016" "l" "x" " must equal obj=" "0x%016" "l" "x", p2i(l_object), p2i (obj)); ::breakpoint(); } } while (0) |
| 643 | INTPTR_FORMAT, p2i(l_object), p2i(obj))do { if (!(l_object == obj)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 643, "assert(" "l_object == obj" ") failed", "object=" "0x%016" "l" "x" " must equal obj=" "0x%016" "l" "x", p2i(l_object), p2i (obj)); ::breakpoint(); } } while (0); |
| 644 | |
| 645 | markWord dmw = header(); |
| 646 | // The dmw has to be neutral (not NULL, not locked and not marked). |
| 647 | assert(dmw.is_neutral(), "must be neutral: dmw=" INTPTR_FORMAT, dmw.value())do { if (!(dmw.is_neutral())) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 647, "assert(" "dmw.is_neutral()" ") failed", "must be neutral: dmw=" "0x%016" "l" "x", dmw.value()); ::breakpoint(); } } while (0 ); |
| 648 | |
| 649 | // Install displaced mark word if the object's header still points |
| 650 | // to this ObjectMonitor. More than one racing caller to this function |
| 651 | // can rarely reach this point, but only one can win. |
| 652 | markWord res = obj->cas_set_mark(dmw, markWord::encode(this)); |
| 653 | if (res != markWord::encode(this)) { |
| 654 | // This should be rare so log at the Info level when it happens. |
| 655 | log_info(monitorinflation)(!(LogImpl<(LogTag::_monitorinflation), (LogTag::__NO_TAG) , (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG)>::is_level(LogLevel::Info))) ? (void)0 : LogImpl<(LogTag::_monitorinflation), (LogTag::__NO_TAG) , (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG)>::write<LogLevel::Info>("install_displaced_markword_in_object: " |
| 656 | "failed cas_set_mark: new_mark=" INTPTR_FORMAT"0x%016" "l" "x" |
| 657 | ", old_mark=" INTPTR_FORMAT"0x%016" "l" "x" ", res=" INTPTR_FORMAT"0x%016" "l" "x", |
| 658 | dmw.value(), markWord::encode(this).value(), |
| 659 | res.value()); |
| 660 | } |
| 661 | |
| 662 | // Note: It does not matter which thread restored the header/dmw |
| 663 | // into the object's header. The thread deflating the monitor just |
| 664 | // wanted the object's header restored and it is. The threads that |
| 665 | // detected a race with the deflation process also wanted the |
| 666 | // object's header restored before they retry their operation and |
| 667 | // because it is restored they will only retry once. |
| 668 | } |
| 669 | |
| 670 | // Convert the fields used by is_busy() to a string that can be |
| 671 | // used for diagnostic output. |
| 672 | const char* ObjectMonitor::is_busy_to_string(stringStream* ss) { |
| 673 | ss->print("is_busy: waiters=%d, ", _waiters); |
| 674 | if (contentions() > 0) { |
| 675 | ss->print("contentions=%d, ", contentions()); |
| 676 | } else { |
| 677 | ss->print("contentions=0"); |
| 678 | } |
| 679 | if (!owner_is_DEFLATER_MARKER()) { |
| 680 | ss->print("owner=" INTPTR_FORMAT"0x%016" "l" "x", p2i(owner_raw())); |
| 681 | } else { |
| 682 | // We report NULL instead of DEFLATER_MARKER here because is_busy() |
| 683 | // ignores DEFLATER_MARKER values. |
| 684 | ss->print("owner=" INTPTR_FORMAT"0x%016" "l" "x", NULL__null); |
| 685 | } |
| 686 | ss->print(", cxq=" INTPTR_FORMAT"0x%016" "l" "x" ", EntryList=" INTPTR_FORMAT"0x%016" "l" "x", p2i(_cxq), |
| 687 | p2i(_EntryList)); |
| 688 | return ss->base(); |
| 689 | } |
| 690 | |
| 691 | #define MAX_RECHECK_INTERVAL1000 1000 |
| 692 | |
| 693 | void ObjectMonitor::EnterI(JavaThread* current) { |
| 694 | assert(current->thread_state() == _thread_blocked, "invariant")do { if (!(current->thread_state() == _thread_blocked)) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 694, "assert(" "current->thread_state() == _thread_blocked" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 695 | |
| 696 | // Try the lock - TATAS |
| 697 | if (TryLock (current) > 0) { |
| 698 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 698, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 699 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 699, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 700 | assert(_Responsible != current, "invariant")do { if (!(_Responsible != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 700, "assert(" "_Responsible != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 701 | return; |
| 702 | } |
| 703 | |
| 704 | if (try_set_owner_from(DEFLATER_MARKERreinterpret_cast<void*>(-1), current) == DEFLATER_MARKERreinterpret_cast<void*>(-1)) { |
| 705 | // Cancelled the in-progress async deflation by changing owner from |
| 706 | // DEFLATER_MARKER to current. As part of the contended enter protocol, |
| 707 | // contentions was incremented to a positive value before EnterI() |
| 708 | // was called and that prevents the deflater thread from winning the |
| 709 | // last part of the 2-part async deflation protocol. After EnterI() |
| 710 | // returns to enter(), contentions is decremented because the caller |
| 711 | // now owns the monitor. We bump contentions an extra time here to |
| 712 | // prevent the deflater thread from winning the last part of the |
| 713 | // 2-part async deflation protocol after the regular decrement |
| 714 | // occurs in enter(). The deflater thread will decrement contentions |
| 715 | // after it recognizes that the async deflation was cancelled. |
| 716 | add_to_contentions(1); |
| 717 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 717, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 718 | assert(_Responsible != current, "invariant")do { if (!(_Responsible != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 718, "assert(" "_Responsible != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 719 | return; |
| 720 | } |
| 721 | |
| 722 | assert(InitDone, "Unexpectedly not initialized")do { if (!(InitDone)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 722, "assert(" "InitDone" ") failed", "Unexpectedly not initialized" ); ::breakpoint(); } } while (0); |
| 723 | |
| 724 | // We try one round of spinning *before* enqueueing current. |
| 725 | // |
| 726 | // If the _owner is ready but OFFPROC we could use a YieldTo() |
| 727 | // operation to donate the remainder of this thread's quantum |
| 728 | // to the owner. This has subtle but beneficial affinity |
| 729 | // effects. |
| 730 | |
| 731 | if (TrySpin(current) > 0) { |
| 732 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 732, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 733 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 733, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 734 | assert(_Responsible != current, "invariant")do { if (!(_Responsible != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 734, "assert(" "_Responsible != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 735 | return; |
| 736 | } |
| 737 | |
| 738 | // The Spin failed -- Enqueue and park the thread ... |
| 739 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 739, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 740 | assert(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 740, "assert(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 741 | assert(_Responsible != current, "invariant")do { if (!(_Responsible != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 741, "assert(" "_Responsible != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 742 | |
| 743 | // Enqueue "current" on ObjectMonitor's _cxq. |
| 744 | // |
| 745 | // Node acts as a proxy for current. |
| 746 | // As an aside, if were to ever rewrite the synchronization code mostly |
| 747 | // in Java, WaitNodes, ObjectMonitors, and Events would become 1st-class |
| 748 | // Java objects. This would avoid awkward lifecycle and liveness issues, |
| 749 | // as well as eliminate a subset of ABA issues. |
| 750 | // TODO: eliminate ObjectWaiter and enqueue either Threads or Events. |
| 751 | |
| 752 | ObjectWaiter node(current); |
| 753 | current->_ParkEvent->reset(); |
| 754 | node._prev = (ObjectWaiter*) 0xBAD; |
| 755 | node.TState = ObjectWaiter::TS_CXQ; |
| 756 | |
| 757 | // Push "current" onto the front of the _cxq. |
| 758 | // Once on cxq/EntryList, current stays on-queue until it acquires the lock. |
| 759 | // Note that spinning tends to reduce the rate at which threads |
| 760 | // enqueue and dequeue on EntryList|cxq. |
| 761 | ObjectWaiter* nxt; |
| 762 | for (;;) { |
| 763 | node._next = nxt = _cxq; |
| 764 | if (Atomic::cmpxchg(&_cxq, nxt, &node) == nxt) break; |
| 765 | |
| 766 | // Interference - the CAS failed because _cxq changed. Just retry. |
| 767 | // As an optional optimization we retry the lock. |
| 768 | if (TryLock (current) > 0) { |
| 769 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 769, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 770 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 770, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 771 | assert(_Responsible != current, "invariant")do { if (!(_Responsible != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 771, "assert(" "_Responsible != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 772 | return; |
| 773 | } |
| 774 | } |
| 775 | |
| 776 | // Check for cxq|EntryList edge transition to non-null. This indicates |
| 777 | // the onset of contention. While contention persists exiting threads |
| 778 | // will use a ST:MEMBAR:LD 1-1 exit protocol. When contention abates exit |
| 779 | // operations revert to the faster 1-0 mode. This enter operation may interleave |
| 780 | // (race) a concurrent 1-0 exit operation, resulting in stranding, so we |
| 781 | // arrange for one of the contending thread to use a timed park() operations |
| 782 | // to detect and recover from the race. (Stranding is form of progress failure |
| 783 | // where the monitor is unlocked but all the contending threads remain parked). |
| 784 | // That is, at least one of the contended threads will periodically poll _owner. |
| 785 | // One of the contending threads will become the designated "Responsible" thread. |
| 786 | // The Responsible thread uses a timed park instead of a normal indefinite park |
| 787 | // operation -- it periodically wakes and checks for and recovers from potential |
| 788 | // strandings admitted by 1-0 exit operations. We need at most one Responsible |
| 789 | // thread per-monitor at any given moment. Only threads on cxq|EntryList may |
| 790 | // be responsible for a monitor. |
| 791 | // |
| 792 | // Currently, one of the contended threads takes on the added role of "Responsible". |
| 793 | // A viable alternative would be to use a dedicated "stranding checker" thread |
| 794 | // that periodically iterated over all the threads (or active monitors) and unparked |
| 795 | // successors where there was risk of stranding. This would help eliminate the |
| 796 | // timer scalability issues we see on some platforms as we'd only have one thread |
| 797 | // -- the checker -- parked on a timer. |
| 798 | |
| 799 | if (nxt == NULL__null && _EntryList == NULL__null) { |
| 800 | // Try to assume the role of responsible thread for the monitor. |
| 801 | // CONSIDER: ST vs CAS vs { if (Responsible==null) Responsible=current } |
| 802 | Atomic::replace_if_null(&_Responsible, current); |
| 803 | } |
| 804 | |
| 805 | // The lock might have been released while this thread was occupied queueing |
| 806 | // itself onto _cxq. To close the race and avoid "stranding" and |
| 807 | // progress-liveness failure we must resample-retry _owner before parking. |
| 808 | // Note the Dekker/Lamport duality: ST cxq; MEMBAR; LD Owner. |
| 809 | // In this case the ST-MEMBAR is accomplished with CAS(). |
| 810 | // |
| 811 | // TODO: Defer all thread state transitions until park-time. |
| 812 | // Since state transitions are heavy and inefficient we'd like |
| 813 | // to defer the state transitions until absolutely necessary, |
| 814 | // and in doing so avoid some transitions ... |
| 815 | |
| 816 | int nWakeups = 0; |
| 817 | int recheckInterval = 1; |
| 818 | |
| 819 | for (;;) { |
| 820 | |
| 821 | if (TryLock(current) > 0) break; |
| 822 | assert(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 822, "assert(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 823 | |
| 824 | // park self |
| 825 | if (_Responsible == current) { |
| 826 | current->_ParkEvent->park((jlong) recheckInterval); |
| 827 | // Increase the recheckInterval, but clamp the value. |
| 828 | recheckInterval *= 8; |
| 829 | if (recheckInterval > MAX_RECHECK_INTERVAL1000) { |
| 830 | recheckInterval = MAX_RECHECK_INTERVAL1000; |
| 831 | } |
| 832 | } else { |
| 833 | current->_ParkEvent->park(); |
| 834 | } |
| 835 | |
| 836 | if (TryLock(current) > 0) break; |
| 837 | |
| 838 | if (try_set_owner_from(DEFLATER_MARKERreinterpret_cast<void*>(-1), current) == DEFLATER_MARKERreinterpret_cast<void*>(-1)) { |
| 839 | // Cancelled the in-progress async deflation by changing owner from |
| 840 | // DEFLATER_MARKER to current. As part of the contended enter protocol, |
| 841 | // contentions was incremented to a positive value before EnterI() |
| 842 | // was called and that prevents the deflater thread from winning the |
| 843 | // last part of the 2-part async deflation protocol. After EnterI() |
| 844 | // returns to enter(), contentions is decremented because the caller |
| 845 | // now owns the monitor. We bump contentions an extra time here to |
| 846 | // prevent the deflater thread from winning the last part of the |
| 847 | // 2-part async deflation protocol after the regular decrement |
| 848 | // occurs in enter(). The deflater thread will decrement contentions |
| 849 | // after it recognizes that the async deflation was cancelled. |
| 850 | add_to_contentions(1); |
| 851 | break; |
| 852 | } |
| 853 | |
| 854 | // The lock is still contested. |
| 855 | // Keep a tally of the # of futile wakeups. |
| 856 | // Note that the counter is not protected by a lock or updated by atomics. |
| 857 | // That is by design - we trade "lossy" counters which are exposed to |
| 858 | // races during updates for a lower probe effect. |
| 859 | |
| 860 | // This PerfData object can be used in parallel with a safepoint. |
| 861 | // See the work around in PerfDataManager::destroy(). |
| 862 | OM_PERFDATA_OP(FutileWakeups, inc())do { if (ObjectMonitor::_sync_FutileWakeups != __null && PerfDataManager::has_PerfData()) { ObjectMonitor::_sync_FutileWakeups ->inc(); } } while (0); |
| 863 | ++nWakeups; |
| 864 | |
| 865 | // Assuming this is not a spurious wakeup we'll normally find _succ == current. |
| 866 | // We can defer clearing _succ until after the spin completes |
| 867 | // TrySpin() must tolerate being called with _succ == current. |
| 868 | // Try yet another round of adaptive spinning. |
| 869 | if (TrySpin(current) > 0) break; |
| 870 | |
| 871 | // We can find that we were unpark()ed and redesignated _succ while |
| 872 | // we were spinning. That's harmless. If we iterate and call park(), |
| 873 | // park() will consume the event and return immediately and we'll |
| 874 | // just spin again. This pattern can repeat, leaving _succ to simply |
| 875 | // spin on a CPU. |
| 876 | |
| 877 | if (_succ == current) _succ = NULL__null; |
| 878 | |
| 879 | // Invariant: after clearing _succ a thread *must* retry _owner before parking. |
| 880 | OrderAccess::fence(); |
| 881 | } |
| 882 | |
| 883 | // Egress : |
| 884 | // current has acquired the lock -- Unlink current from the cxq or EntryList. |
| 885 | // Normally we'll find current on the EntryList . |
| 886 | // From the perspective of the lock owner (this thread), the |
| 887 | // EntryList is stable and cxq is prepend-only. |
| 888 | // The head of cxq is volatile but the interior is stable. |
| 889 | // In addition, current.TState is stable. |
| 890 | |
| 891 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 891, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 892 | |
| 893 | UnlinkAfterAcquire(current, &node); |
| 894 | if (_succ == current) _succ = NULL__null; |
| 895 | |
| 896 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 896, "assert(" "_succ != current" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 897 | if (_Responsible == current) { |
| 898 | _Responsible = NULL__null; |
| 899 | OrderAccess::fence(); // Dekker pivot-point |
| 900 | |
| 901 | // We may leave threads on cxq|EntryList without a designated |
| 902 | // "Responsible" thread. This is benign. When this thread subsequently |
| 903 | // exits the monitor it can "see" such preexisting "old" threads -- |
| 904 | // threads that arrived on the cxq|EntryList before the fence, above -- |
| 905 | // by LDing cxq|EntryList. Newly arrived threads -- that is, threads |
| 906 | // that arrive on cxq after the ST:MEMBAR, above -- will set Responsible |
| 907 | // non-null and elect a new "Responsible" timer thread. |
| 908 | // |
| 909 | // This thread executes: |
| 910 | // ST Responsible=null; MEMBAR (in enter epilogue - here) |
| 911 | // LD cxq|EntryList (in subsequent exit) |
| 912 | // |
| 913 | // Entering threads in the slow/contended path execute: |
| 914 | // ST cxq=nonnull; MEMBAR; LD Responsible (in enter prolog) |
| 915 | // The (ST cxq; MEMBAR) is accomplished with CAS(). |
| 916 | // |
| 917 | // The MEMBAR, above, prevents the LD of cxq|EntryList in the subsequent |
| 918 | // exit operation from floating above the ST Responsible=null. |
| 919 | } |
| 920 | |
| 921 | // We've acquired ownership with CAS(). |
| 922 | // CAS is serializing -- it has MEMBAR/FENCE-equivalent semantics. |
| 923 | // But since the CAS() this thread may have also stored into _succ, |
| 924 | // EntryList, cxq or Responsible. These meta-data updates must be |
| 925 | // visible __before this thread subsequently drops the lock. |
| 926 | // Consider what could occur if we didn't enforce this constraint -- |
| 927 | // STs to monitor meta-data and user-data could reorder with (become |
| 928 | // visible after) the ST in exit that drops ownership of the lock. |
| 929 | // Some other thread could then acquire the lock, but observe inconsistent |
| 930 | // or old monitor meta-data and heap data. That violates the JMM. |
| 931 | // To that end, the 1-0 exit() operation must have at least STST|LDST |
| 932 | // "release" barrier semantics. Specifically, there must be at least a |
| 933 | // STST|LDST barrier in exit() before the ST of null into _owner that drops |
| 934 | // the lock. The barrier ensures that changes to monitor meta-data and data |
| 935 | // protected by the lock will be visible before we release the lock, and |
| 936 | // therefore before some other thread (CPU) has a chance to acquire the lock. |
| 937 | // See also: http://gee.cs.oswego.edu/dl/jmm/cookbook.html. |
| 938 | // |
| 939 | // Critically, any prior STs to _succ or EntryList must be visible before |
| 940 | // the ST of null into _owner in the *subsequent* (following) corresponding |
| 941 | // monitorexit. Recall too, that in 1-0 mode monitorexit does not necessarily |
| 942 | // execute a serializing instruction. |
| 943 | |
| 944 | return; |
| 945 | } |
| 946 | |
| 947 | // ReenterI() is a specialized inline form of the latter half of the |
| 948 | // contended slow-path from EnterI(). We use ReenterI() only for |
| 949 | // monitor reentry in wait(). |
| 950 | // |
| 951 | // In the future we should reconcile EnterI() and ReenterI(). |
| 952 | |
| 953 | void ObjectMonitor::ReenterI(JavaThread* current, ObjectWaiter* currentNode) { |
| 954 | assert(current != NULL, "invariant")do { if (!(current != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 954, "assert(" "current != __null" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 955 | assert(currentNode != NULL, "invariant")do { if (!(currentNode != __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 955, "assert(" "currentNode != __null" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 956 | assert(currentNode->_thread == current, "invariant")do { if (!(currentNode->_thread == current)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 956, "assert(" "currentNode->_thread == current" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 957 | assert(_waiters > 0, "invariant")do { if (!(_waiters > 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 957, "assert(" "_waiters > 0" ") failed", "invariant"); :: breakpoint(); } } while (0); |
| 958 | assert(object()->mark() == markWord::encode(this), "invariant")do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 958, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 959 | |
| 960 | assert(current->thread_state() != _thread_blocked, "invariant")do { if (!(current->thread_state() != _thread_blocked)) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 960, "assert(" "current->thread_state() != _thread_blocked" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 961 | |
| 962 | int nWakeups = 0; |
| 963 | for (;;) { |
| 964 | ObjectWaiter::TStates v = currentNode->TState; |
| 965 | guarantee(v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ, "invariant")do { if (!(v == ObjectWaiter::TS_ENTER || v == ObjectWaiter:: TS_CXQ)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 965, "guarantee(" "v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 966 | assert(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 966, "assert(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 967 | |
| 968 | if (TryLock(current) > 0) break; |
| 969 | if (TrySpin(current) > 0) break; |
| 970 | |
| 971 | { |
| 972 | OSThreadContendState osts(current->osthread()); |
| 973 | |
| 974 | assert(current->thread_state() == _thread_in_vm, "invariant")do { if (!(current->thread_state() == _thread_in_vm)) { (* g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 974, "assert(" "current->thread_state() == _thread_in_vm" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 975 | |
| 976 | { |
| 977 | ClearSuccOnSuspend csos(this); |
| 978 | ThreadBlockInVMPreprocess<ClearSuccOnSuspend> tbivs(current, csos, true /* allow_suspend */); |
| 979 | current->_ParkEvent->park(); |
| 980 | } |
| 981 | } |
| 982 | |
| 983 | // Try again, but just so we distinguish between futile wakeups and |
| 984 | // successful wakeups. The following test isn't algorithmically |
| 985 | // necessary, but it helps us maintain sensible statistics. |
| 986 | if (TryLock(current) > 0) break; |
| 987 | |
| 988 | // The lock is still contested. |
| 989 | // Keep a tally of the # of futile wakeups. |
| 990 | // Note that the counter is not protected by a lock or updated by atomics. |
| 991 | // That is by design - we trade "lossy" counters which are exposed to |
| 992 | // races during updates for a lower probe effect. |
| 993 | ++nWakeups; |
| 994 | |
| 995 | // Assuming this is not a spurious wakeup we'll normally |
| 996 | // find that _succ == current. |
| 997 | if (_succ == current) _succ = NULL__null; |
| 998 | |
| 999 | // Invariant: after clearing _succ a contending thread |
| 1000 | // *must* retry _owner before parking. |
| 1001 | OrderAccess::fence(); |
| 1002 | |
| 1003 | // This PerfData object can be used in parallel with a safepoint. |
| 1004 | // See the work around in PerfDataManager::destroy(). |
| 1005 | OM_PERFDATA_OP(FutileWakeups, inc())do { if (ObjectMonitor::_sync_FutileWakeups != __null && PerfDataManager::has_PerfData()) { ObjectMonitor::_sync_FutileWakeups ->inc(); } } while (0); |
| 1006 | } |
| 1007 | |
| 1008 | // current has acquired the lock -- Unlink current from the cxq or EntryList . |
| 1009 | // Normally we'll find current on the EntryList. |
| 1010 | // Unlinking from the EntryList is constant-time and atomic-free. |
| 1011 | // From the perspective of the lock owner (this thread), the |
| 1012 | // EntryList is stable and cxq is prepend-only. |
| 1013 | // The head of cxq is volatile but the interior is stable. |
| 1014 | // In addition, current.TState is stable. |
| 1015 | |
| 1016 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1016, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1017 | assert(object()->mark() == markWord::encode(this), "invariant")do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1017, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1018 | UnlinkAfterAcquire(current, currentNode); |
| 1019 | if (_succ == current) _succ = NULL__null; |
| 1020 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1020, "assert(" "_succ != current" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1021 | currentNode->TState = ObjectWaiter::TS_RUN; |
| 1022 | OrderAccess::fence(); // see comments at the end of EnterI() |
| 1023 | } |
| 1024 | |
| 1025 | // By convention we unlink a contending thread from EntryList|cxq immediately |
| 1026 | // after the thread acquires the lock in ::enter(). Equally, we could defer |
| 1027 | // unlinking the thread until ::exit()-time. |
| 1028 | |
| 1029 | void ObjectMonitor::UnlinkAfterAcquire(JavaThread* current, ObjectWaiter* currentNode) { |
| 1030 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1030, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1031 | assert(currentNode->_thread == current, "invariant")do { if (!(currentNode->_thread == current)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1031, "assert(" "currentNode->_thread == current" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1032 | |
| 1033 | if (currentNode->TState == ObjectWaiter::TS_ENTER) { |
| 1034 | // Normal case: remove current from the DLL EntryList . |
| 1035 | // This is a constant-time operation. |
| 1036 | ObjectWaiter* nxt = currentNode->_next; |
| 1037 | ObjectWaiter* prv = currentNode->_prev; |
| 1038 | if (nxt != NULL__null) nxt->_prev = prv; |
| 1039 | if (prv != NULL__null) prv->_next = nxt; |
| 1040 | if (currentNode == _EntryList) _EntryList = nxt; |
| 1041 | assert(nxt == NULL || nxt->TState == ObjectWaiter::TS_ENTER, "invariant")do { if (!(nxt == __null || nxt->TState == ObjectWaiter::TS_ENTER )) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1041, "assert(" "nxt == __null || nxt->TState == ObjectWaiter::TS_ENTER" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1042 | assert(prv == NULL || prv->TState == ObjectWaiter::TS_ENTER, "invariant")do { if (!(prv == __null || prv->TState == ObjectWaiter::TS_ENTER )) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1042, "assert(" "prv == __null || prv->TState == ObjectWaiter::TS_ENTER" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1043 | } else { |
| 1044 | assert(currentNode->TState == ObjectWaiter::TS_CXQ, "invariant")do { if (!(currentNode->TState == ObjectWaiter::TS_CXQ)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1044, "assert(" "currentNode->TState == ObjectWaiter::TS_CXQ" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1045 | // Inopportune interleaving -- current is still on the cxq. |
| 1046 | // This usually means the enqueue of self raced an exiting thread. |
| 1047 | // Normally we'll find current near the front of the cxq, so |
| 1048 | // dequeueing is typically fast. If needbe we can accelerate |
| 1049 | // this with some MCS/CHL-like bidirectional list hints and advisory |
| 1050 | // back-links so dequeueing from the interior will normally operate |
| 1051 | // in constant-time. |
| 1052 | // Dequeue current from either the head (with CAS) or from the interior |
| 1053 | // with a linear-time scan and normal non-atomic memory operations. |
| 1054 | // CONSIDER: if current is on the cxq then simply drain cxq into EntryList |
| 1055 | // and then unlink current from EntryList. We have to drain eventually, |
| 1056 | // so it might as well be now. |
| 1057 | |
| 1058 | ObjectWaiter* v = _cxq; |
| 1059 | assert(v != NULL, "invariant")do { if (!(v != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1059, "assert(" "v != __null" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 1060 | if (v != currentNode || Atomic::cmpxchg(&_cxq, v, currentNode->_next) != v) { |
| 1061 | // The CAS above can fail from interference IFF a "RAT" arrived. |
| 1062 | // In that case current must be in the interior and can no longer be |
| 1063 | // at the head of cxq. |
| 1064 | if (v == currentNode) { |
| 1065 | assert(_cxq != v, "invariant")do { if (!(_cxq != v)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1065, "assert(" "_cxq != v" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 1066 | v = _cxq; // CAS above failed - start scan at head of list |
| 1067 | } |
| 1068 | ObjectWaiter* p; |
| 1069 | ObjectWaiter* q = NULL__null; |
| 1070 | for (p = v; p != NULL__null && p != currentNode; p = p->_next) { |
| 1071 | q = p; |
| 1072 | assert(p->TState == ObjectWaiter::TS_CXQ, "invariant")do { if (!(p->TState == ObjectWaiter::TS_CXQ)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1072, "assert(" "p->TState == ObjectWaiter::TS_CXQ" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1073 | } |
| 1074 | assert(v != currentNode, "invariant")do { if (!(v != currentNode)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1074, "assert(" "v != currentNode" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1075 | assert(p == currentNode, "Node not found on cxq")do { if (!(p == currentNode)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1075, "assert(" "p == currentNode" ") failed", "Node not found on cxq" ); ::breakpoint(); } } while (0); |
| 1076 | assert(p != _cxq, "invariant")do { if (!(p != _cxq)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1076, "assert(" "p != _cxq" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 1077 | assert(q != NULL, "invariant")do { if (!(q != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1077, "assert(" "q != __null" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 1078 | assert(q->_next == p, "invariant")do { if (!(q->_next == p)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1078, "assert(" "q->_next == p" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1079 | q->_next = p->_next; |
| 1080 | } |
| 1081 | } |
| 1082 | |
| 1083 | #ifdef ASSERT1 |
| 1084 | // Diagnostic hygiene ... |
| 1085 | currentNode->_prev = (ObjectWaiter*) 0xBAD; |
| 1086 | currentNode->_next = (ObjectWaiter*) 0xBAD; |
| 1087 | currentNode->TState = ObjectWaiter::TS_RUN; |
| 1088 | #endif |
| 1089 | } |
| 1090 | |
| 1091 | // ----------------------------------------------------------------------------- |
| 1092 | // Exit support |
| 1093 | // |
| 1094 | // exit() |
| 1095 | // ~~~~~~ |
| 1096 | // Note that the collector can't reclaim the objectMonitor or deflate |
| 1097 | // the object out from underneath the thread calling ::exit() as the |
| 1098 | // thread calling ::exit() never transitions to a stable state. |
| 1099 | // This inhibits GC, which in turn inhibits asynchronous (and |
| 1100 | // inopportune) reclamation of "this". |
| 1101 | // |
| 1102 | // We'd like to assert that: (THREAD->thread_state() != _thread_blocked) ; |
| 1103 | // There's one exception to the claim above, however. EnterI() can call |
| 1104 | // exit() to drop a lock if the acquirer has been externally suspended. |
| 1105 | // In that case exit() is called with _thread_state == _thread_blocked, |
| 1106 | // but the monitor's _contentions field is > 0, which inhibits reclamation. |
| 1107 | // |
| 1108 | // 1-0 exit |
| 1109 | // ~~~~~~~~ |
| 1110 | // ::exit() uses a canonical 1-1 idiom with a MEMBAR although some of |
| 1111 | // the fast-path operators have been optimized so the common ::exit() |
| 1112 | // operation is 1-0, e.g., see macroAssembler_x86.cpp: fast_unlock(). |
| 1113 | // The code emitted by fast_unlock() elides the usual MEMBAR. This |
| 1114 | // greatly improves latency -- MEMBAR and CAS having considerable local |
| 1115 | // latency on modern processors -- but at the cost of "stranding". Absent the |
| 1116 | // MEMBAR, a thread in fast_unlock() can race a thread in the slow |
| 1117 | // ::enter() path, resulting in the entering thread being stranding |
| 1118 | // and a progress-liveness failure. Stranding is extremely rare. |
| 1119 | // We use timers (timed park operations) & periodic polling to detect |
| 1120 | // and recover from stranding. Potentially stranded threads periodically |
| 1121 | // wake up and poll the lock. See the usage of the _Responsible variable. |
| 1122 | // |
| 1123 | // The CAS() in enter provides for safety and exclusion, while the CAS or |
| 1124 | // MEMBAR in exit provides for progress and avoids stranding. 1-0 locking |
| 1125 | // eliminates the CAS/MEMBAR from the exit path, but it admits stranding. |
| 1126 | // We detect and recover from stranding with timers. |
| 1127 | // |
| 1128 | // If a thread transiently strands it'll park until (a) another |
| 1129 | // thread acquires the lock and then drops the lock, at which time the |
| 1130 | // exiting thread will notice and unpark the stranded thread, or, (b) |
| 1131 | // the timer expires. If the lock is high traffic then the stranding latency |
| 1132 | // will be low due to (a). If the lock is low traffic then the odds of |
| 1133 | // stranding are lower, although the worst-case stranding latency |
| 1134 | // is longer. Critically, we don't want to put excessive load in the |
| 1135 | // platform's timer subsystem. We want to minimize both the timer injection |
| 1136 | // rate (timers created/sec) as well as the number of timers active at |
| 1137 | // any one time. (more precisely, we want to minimize timer-seconds, which is |
| 1138 | // the integral of the # of active timers at any instant over time). |
| 1139 | // Both impinge on OS scalability. Given that, at most one thread parked on |
| 1140 | // a monitor will use a timer. |
| 1141 | // |
| 1142 | // There is also the risk of a futile wake-up. If we drop the lock |
| 1143 | // another thread can reacquire the lock immediately, and we can |
| 1144 | // then wake a thread unnecessarily. This is benign, and we've |
| 1145 | // structured the code so the windows are short and the frequency |
| 1146 | // of such futile wakups is low. |
| 1147 | |
| 1148 | void ObjectMonitor::exit(JavaThread* current, bool not_suspended) { |
| 1149 | void* cur = owner_raw(); |
| 1150 | if (current != cur) { |
| 1151 | if (current->is_lock_owned((address)cur)) { |
| 1152 | assert(_recursions == 0, "invariant")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1152, "assert(" "_recursions == 0" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1153 | set_owner_from_BasicLock(cur, current); // Convert from BasicLock* to Thread*. |
| 1154 | _recursions = 0; |
| 1155 | } else { |
| 1156 | // Apparent unbalanced locking ... |
| 1157 | // Naively we'd like to throw IllegalMonitorStateException. |
| 1158 | // As a practical matter we can neither allocate nor throw an |
| 1159 | // exception as ::exit() can be called from leaf routines. |
| 1160 | // see x86_32.ad Fast_Unlock() and the I1 and I2 properties. |
| 1161 | // Upon deeper reflection, however, in a properly run JVM the only |
| 1162 | // way we should encounter this situation is in the presence of |
| 1163 | // unbalanced JNI locking. TODO: CheckJNICalls. |
| 1164 | // See also: CR4414101 |
| 1165 | #ifdef ASSERT1 |
| 1166 | LogStreamHandle(Error, monitorinflation)LogStreamTemplate<LogLevel::Error, (LogTag::_monitorinflation ), (LogTag::__NO_TAG), (LogTag::__NO_TAG), (LogTag::__NO_TAG) , (LogTag::__NO_TAG), (LogTag::__NO_TAG)> lsh; |
| 1167 | lsh.print_cr("ERROR: ObjectMonitor::exit(): thread=" INTPTR_FORMAT"0x%016" "l" "x" |
| 1168 | " is exiting an ObjectMonitor it does not own.", p2i(current)); |
| 1169 | lsh.print_cr("The imbalance is possibly caused by JNI locking."); |
| 1170 | print_debug_style_on(&lsh); |
| 1171 | assert(false, "Non-balanced monitor enter/exit!")do { if (!(false)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1171, "assert(" "false" ") failed", "Non-balanced monitor enter/exit!" ); ::breakpoint(); } } while (0); |
| 1172 | #endif |
| 1173 | return; |
| 1174 | } |
| 1175 | } |
| 1176 | |
| 1177 | if (_recursions != 0) { |
| 1178 | _recursions--; // this is simple recursive enter |
| 1179 | return; |
| 1180 | } |
| 1181 | |
| 1182 | // Invariant: after setting Responsible=null an thread must execute |
| 1183 | // a MEMBAR or other serializing instruction before fetching EntryList|cxq. |
| 1184 | _Responsible = NULL__null; |
| 1185 | |
| 1186 | #if INCLUDE_JFR1 |
| 1187 | // get the owner's thread id for the MonitorEnter event |
| 1188 | // if it is enabled and the thread isn't suspended |
| 1189 | if (not_suspended && EventJavaMonitorEnter::is_enabled()) { |
| 1190 | _previous_owner_tid = JFR_THREAD_ID(current)((current)->jfr_thread_local()->thread_id()); |
| 1191 | } |
| 1192 | #endif |
| 1193 | |
| 1194 | for (;;) { |
| 1195 | assert(current == owner_raw(), "invariant")do { if (!(current == owner_raw())) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1195, "assert(" "current == owner_raw()" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1196 | |
| 1197 | // Drop the lock. |
| 1198 | // release semantics: prior loads and stores from within the critical section |
| 1199 | // must not float (reorder) past the following store that drops the lock. |
| 1200 | // Uses a storeload to separate release_store(owner) from the |
| 1201 | // successor check. The try_set_owner() below uses cmpxchg() so |
| 1202 | // we get the fence down there. |
| 1203 | release_clear_owner(current); |
| 1204 | OrderAccess::storeload(); |
| 1205 | |
| 1206 | if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL__null) { |
| 1207 | return; |
| 1208 | } |
| 1209 | // Other threads are blocked trying to acquire the lock. |
| 1210 | |
| 1211 | // Normally the exiting thread is responsible for ensuring succession, |
| 1212 | // but if other successors are ready or other entering threads are spinning |
| 1213 | // then this thread can simply store NULL into _owner and exit without |
| 1214 | // waking a successor. The existence of spinners or ready successors |
| 1215 | // guarantees proper succession (liveness). Responsibility passes to the |
| 1216 | // ready or running successors. The exiting thread delegates the duty. |
| 1217 | // More precisely, if a successor already exists this thread is absolved |
| 1218 | // of the responsibility of waking (unparking) one. |
| 1219 | // |
| 1220 | // The _succ variable is critical to reducing futile wakeup frequency. |
| 1221 | // _succ identifies the "heir presumptive" thread that has been made |
| 1222 | // ready (unparked) but that has not yet run. We need only one such |
| 1223 | // successor thread to guarantee progress. |
| 1224 | // See http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf |
| 1225 | // section 3.3 "Futile Wakeup Throttling" for details. |
| 1226 | // |
| 1227 | // Note that spinners in Enter() also set _succ non-null. |
| 1228 | // In the current implementation spinners opportunistically set |
| 1229 | // _succ so that exiting threads might avoid waking a successor. |
| 1230 | // Another less appealing alternative would be for the exiting thread |
| 1231 | // to drop the lock and then spin briefly to see if a spinner managed |
| 1232 | // to acquire the lock. If so, the exiting thread could exit |
| 1233 | // immediately without waking a successor, otherwise the exiting |
| 1234 | // thread would need to dequeue and wake a successor. |
| 1235 | // (Note that we'd need to make the post-drop spin short, but no |
| 1236 | // shorter than the worst-case round-trip cache-line migration time. |
| 1237 | // The dropped lock needs to become visible to the spinner, and then |
| 1238 | // the acquisition of the lock by the spinner must become visible to |
| 1239 | // the exiting thread). |
| 1240 | |
| 1241 | // It appears that an heir-presumptive (successor) must be made ready. |
| 1242 | // Only the current lock owner can manipulate the EntryList or |
| 1243 | // drain _cxq, so we need to reacquire the lock. If we fail |
| 1244 | // to reacquire the lock the responsibility for ensuring succession |
| 1245 | // falls to the new owner. |
| 1246 | // |
| 1247 | if (try_set_owner_from(NULL__null, current) != NULL__null) { |
| 1248 | return; |
| 1249 | } |
| 1250 | |
| 1251 | guarantee(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1251, "guarantee(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1252 | |
| 1253 | ObjectWaiter* w = NULL__null; |
| 1254 | |
| 1255 | w = _EntryList; |
| 1256 | if (w != NULL__null) { |
| 1257 | // I'd like to write: guarantee (w->_thread != current). |
| 1258 | // But in practice an exiting thread may find itself on the EntryList. |
| 1259 | // Let's say thread T1 calls O.wait(). Wait() enqueues T1 on O's waitset and |
| 1260 | // then calls exit(). Exit release the lock by setting O._owner to NULL. |
| 1261 | // Let's say T1 then stalls. T2 acquires O and calls O.notify(). The |
| 1262 | // notify() operation moves T1 from O's waitset to O's EntryList. T2 then |
| 1263 | // release the lock "O". T2 resumes immediately after the ST of null into |
| 1264 | // _owner, above. T2 notices that the EntryList is populated, so it |
| 1265 | // reacquires the lock and then finds itself on the EntryList. |
| 1266 | // Given all that, we have to tolerate the circumstance where "w" is |
| 1267 | // associated with current. |
| 1268 | assert(w->TState == ObjectWaiter::TS_ENTER, "invariant")do { if (!(w->TState == ObjectWaiter::TS_ENTER)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1268, "assert(" "w->TState == ObjectWaiter::TS_ENTER" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1269 | ExitEpilog(current, w); |
| 1270 | return; |
| 1271 | } |
| 1272 | |
| 1273 | // If we find that both _cxq and EntryList are null then just |
| 1274 | // re-run the exit protocol from the top. |
| 1275 | w = _cxq; |
| 1276 | if (w == NULL__null) continue; |
| 1277 | |
| 1278 | // Drain _cxq into EntryList - bulk transfer. |
| 1279 | // First, detach _cxq. |
| 1280 | // The following loop is tantamount to: w = swap(&cxq, NULL) |
| 1281 | for (;;) { |
| 1282 | assert(w != NULL, "Invariant")do { if (!(w != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1282, "assert(" "w != __null" ") failed", "Invariant"); ::breakpoint (); } } while (0); |
| 1283 | ObjectWaiter* u = Atomic::cmpxchg(&_cxq, w, (ObjectWaiter*)NULL__null); |
| 1284 | if (u == w) break; |
| 1285 | w = u; |
| 1286 | } |
| 1287 | |
| 1288 | assert(w != NULL, "invariant")do { if (!(w != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1288, "assert(" "w != __null" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 1289 | assert(_EntryList == NULL, "invariant")do { if (!(_EntryList == __null)) { (*g_assert_poison) = 'X'; ; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1289, "assert(" "_EntryList == __null" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1290 | |
| 1291 | // Convert the LIFO SLL anchored by _cxq into a DLL. |
| 1292 | // The list reorganization step operates in O(LENGTH(w)) time. |
| 1293 | // It's critical that this step operate quickly as |
| 1294 | // "current" still holds the outer-lock, restricting parallelism |
| 1295 | // and effectively lengthening the critical section. |
| 1296 | // Invariant: s chases t chases u. |
| 1297 | // TODO-FIXME: consider changing EntryList from a DLL to a CDLL so |
| 1298 | // we have faster access to the tail. |
| 1299 | |
| 1300 | _EntryList = w; |
| 1301 | ObjectWaiter* q = NULL__null; |
| 1302 | ObjectWaiter* p; |
| 1303 | for (p = w; p != NULL__null; p = p->_next) { |
| 1304 | guarantee(p->TState == ObjectWaiter::TS_CXQ, "Invariant")do { if (!(p->TState == ObjectWaiter::TS_CXQ)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1304, "guarantee(" "p->TState == ObjectWaiter::TS_CXQ" ") failed" , "Invariant"); ::breakpoint(); } } while (0); |
| 1305 | p->TState = ObjectWaiter::TS_ENTER; |
| 1306 | p->_prev = q; |
| 1307 | q = p; |
| 1308 | } |
| 1309 | |
| 1310 | // In 1-0 mode we need: ST EntryList; MEMBAR #storestore; ST _owner = NULL |
| 1311 | // The MEMBAR is satisfied by the release_store() operation in ExitEpilog(). |
| 1312 | |
| 1313 | // See if we can abdicate to a spinner instead of waking a thread. |
| 1314 | // A primary goal of the implementation is to reduce the |
| 1315 | // context-switch rate. |
| 1316 | if (_succ != NULL__null) continue; |
| 1317 | |
| 1318 | w = _EntryList; |
| 1319 | if (w != NULL__null) { |
| 1320 | guarantee(w->TState == ObjectWaiter::TS_ENTER, "invariant")do { if (!(w->TState == ObjectWaiter::TS_ENTER)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1320, "guarantee(" "w->TState == ObjectWaiter::TS_ENTER" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1321 | ExitEpilog(current, w); |
| 1322 | return; |
| 1323 | } |
| 1324 | } |
| 1325 | } |
| 1326 | |
| 1327 | void ObjectMonitor::ExitEpilog(JavaThread* current, ObjectWaiter* Wakee) { |
| 1328 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1328, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1329 | |
| 1330 | // Exit protocol: |
| 1331 | // 1. ST _succ = wakee |
| 1332 | // 2. membar #loadstore|#storestore; |
| 1333 | // 2. ST _owner = NULL |
| 1334 | // 3. unpark(wakee) |
| 1335 | |
| 1336 | _succ = Wakee->_thread; |
| 1337 | ParkEvent * Trigger = Wakee->_event; |
| 1338 | |
| 1339 | // Hygiene -- once we've set _owner = NULL we can't safely dereference Wakee again. |
| 1340 | // The thread associated with Wakee may have grabbed the lock and "Wakee" may be |
| 1341 | // out-of-scope (non-extant). |
| 1342 | Wakee = NULL__null; |
| 1343 | |
| 1344 | // Drop the lock. |
| 1345 | // Uses a fence to separate release_store(owner) from the LD in unpark(). |
| 1346 | release_clear_owner(current); |
| 1347 | OrderAccess::fence(); |
| 1348 | |
| 1349 | DTRACE_MONITOR_PROBE(contended__exit, this, object(), current){;}; |
| 1350 | Trigger->unpark(); |
| 1351 | |
| 1352 | // Maintain stats and report events to JVMTI |
| 1353 | OM_PERFDATA_OP(Parks, inc())do { if (ObjectMonitor::_sync_Parks != __null && PerfDataManager ::has_PerfData()) { ObjectMonitor::_sync_Parks->inc(); } } while (0); |
| 1354 | } |
| 1355 | |
| 1356 | |
| 1357 | // ----------------------------------------------------------------------------- |
| 1358 | // Class Loader deadlock handling. |
| 1359 | // |
| 1360 | // complete_exit exits a lock returning recursion count |
| 1361 | // complete_exit/reenter operate as a wait without waiting |
| 1362 | // complete_exit requires an inflated monitor |
| 1363 | // The _owner field is not always the Thread addr even with an |
| 1364 | // inflated monitor, e.g. the monitor can be inflated by a non-owning |
| 1365 | // thread due to contention. |
| 1366 | intx ObjectMonitor::complete_exit(JavaThread* current) { |
| 1367 | assert(InitDone, "Unexpectedly not initialized")do { if (!(InitDone)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1367, "assert(" "InitDone" ") failed", "Unexpectedly not initialized" ); ::breakpoint(); } } while (0); |
| 1368 | |
| 1369 | void* cur = owner_raw(); |
| 1370 | if (current != cur) { |
| 1371 | if (current->is_lock_owned((address)cur)) { |
| 1372 | assert(_recursions == 0, "internal state error")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1372, "assert(" "_recursions == 0" ") failed", "internal state error" ); ::breakpoint(); } } while (0); |
| 1373 | set_owner_from_BasicLock(cur, current); // Convert from BasicLock* to Thread*. |
| 1374 | _recursions = 0; |
| 1375 | } |
| 1376 | } |
| 1377 | |
| 1378 | guarantee(current == owner_raw(), "complete_exit not owner")do { if (!(current == owner_raw())) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1378, "guarantee(" "current == owner_raw()" ") failed", "complete_exit not owner" ); ::breakpoint(); } } while (0); |
| 1379 | intx save = _recursions; // record the old recursion count |
| 1380 | _recursions = 0; // set the recursion level to be 0 |
| 1381 | exit(current); // exit the monitor |
| 1382 | guarantee(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1382, "guarantee(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1383 | return save; |
| 1384 | } |
| 1385 | |
| 1386 | // reenter() enters a lock and sets recursion count |
| 1387 | // complete_exit/reenter operate as a wait without waiting |
| 1388 | bool ObjectMonitor::reenter(intx recursions, JavaThread* current) { |
| 1389 | |
| 1390 | guarantee(owner_raw() != current, "reenter already owner")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1390, "guarantee(" "owner_raw() != current" ") failed", "reenter already owner" ); ::breakpoint(); } } while (0); |
| 1391 | if (!enter(current)) { |
| 1392 | return false; |
| 1393 | } |
| 1394 | // Entered the monitor. |
| 1395 | guarantee(_recursions == 0, "reenter recursion")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1395, "guarantee(" "_recursions == 0" ") failed", "reenter recursion" ); ::breakpoint(); } } while (0); |
| 1396 | _recursions = recursions; |
| 1397 | return true; |
| 1398 | } |
| 1399 | |
| 1400 | // Checks that the current THREAD owns this monitor and causes an |
| 1401 | // immediate return if it doesn't. We don't use the CHECK macro |
| 1402 | // because we want the IMSE to be the only exception that is thrown |
| 1403 | // from the call site when false is returned. Any other pending |
| 1404 | // exception is ignored. |
| 1405 | #define CHECK_OWNER()do { if (!check_owner(__the_thread__)) { do { if (!((((ThreadShadow *)__the_thread__)->has_pending_exception()))) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1405, "assert(" "(((ThreadShadow*)__the_thread__)->has_pending_exception())" ") failed", "expected a pending IMSE here."); ::breakpoint() ; } } while (0); return; } } while (false) \ |
| 1406 | do { \ |
| 1407 | if (!check_owner(THREAD__the_thread__)) { \ |
| 1408 | assert(HAS_PENDING_EXCEPTION, "expected a pending IMSE here.")do { if (!((((ThreadShadow*)__the_thread__)->has_pending_exception ()))) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1408, "assert(" "(((ThreadShadow*)__the_thread__)->has_pending_exception())" ") failed", "expected a pending IMSE here."); ::breakpoint() ; } } while (0); \ |
| 1409 | return; \ |
| 1410 | } \ |
| 1411 | } while (false) |
| 1412 | |
| 1413 | // Returns true if the specified thread owns the ObjectMonitor. |
| 1414 | // Otherwise returns false and throws IllegalMonitorStateException |
| 1415 | // (IMSE). If there is a pending exception and the specified thread |
| 1416 | // is not the owner, that exception will be replaced by the IMSE. |
| 1417 | bool ObjectMonitor::check_owner(TRAPSJavaThread* __the_thread__) { |
| 1418 | JavaThread* current = THREAD__the_thread__; |
| 1419 | void* cur = owner_raw(); |
| 1420 | if (cur == current) { |
| 1421 | return true; |
| 1422 | } |
| 1423 | if (current->is_lock_owned((address)cur)) { |
| 1424 | set_owner_from_BasicLock(cur, current); // Convert from BasicLock* to Thread*. |
| 1425 | _recursions = 0; |
| 1426 | return true; |
| 1427 | } |
| 1428 | THROW_MSG_(vmSymbols::java_lang_IllegalMonitorStateException(),{ Exceptions::_throw_msg(__the_thread__, "/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1429, vmSymbols::java_lang_IllegalMonitorStateException(), "current thread is not owner" ); return false; } |
| 1429 | "current thread is not owner", false){ Exceptions::_throw_msg(__the_thread__, "/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1429, vmSymbols::java_lang_IllegalMonitorStateException(), "current thread is not owner" ); return false; }; |
| 1430 | } |
| 1431 | |
| 1432 | static void post_monitor_wait_event(EventJavaMonitorWait* event, |
| 1433 | ObjectMonitor* monitor, |
| 1434 | uint64_t notifier_tid, |
| 1435 | jlong timeout, |
| 1436 | bool timedout) { |
| 1437 | assert(event != NULL, "invariant")do { if (!(event != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1437, "assert(" "event != __null" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1438 | assert(monitor != NULL, "invariant")do { if (!(monitor != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1438, "assert(" "monitor != __null" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1439 | event->set_monitorClass(monitor->object()->klass()); |
| 1440 | event->set_timeout(timeout); |
| 1441 | // Set an address that is 'unique enough', such that events close in |
| 1442 | // time and with the same address are likely (but not guaranteed) to |
| 1443 | // belong to the same object. |
| 1444 | event->set_address((uintptr_t)monitor); |
| 1445 | event->set_notifier(notifier_tid); |
| 1446 | event->set_timedOut(timedout); |
| 1447 | event->commit(); |
| 1448 | } |
| 1449 | |
| 1450 | // ----------------------------------------------------------------------------- |
| 1451 | // Wait/Notify/NotifyAll |
| 1452 | // |
| 1453 | // Note: a subset of changes to ObjectMonitor::wait() |
| 1454 | // will need to be replicated in complete_exit |
| 1455 | void ObjectMonitor::wait(jlong millis, bool interruptible, TRAPSJavaThread* __the_thread__) { |
| 1456 | JavaThread* current = THREAD__the_thread__; |
| 1457 | |
| 1458 | assert(InitDone, "Unexpectedly not initialized")do { if (!(InitDone)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1458, "assert(" "InitDone" ") failed", "Unexpectedly not initialized" ); ::breakpoint(); } } while (0); |
| 1459 | |
| 1460 | CHECK_OWNER()do { if (!check_owner(__the_thread__)) { do { if (!((((ThreadShadow *)__the_thread__)->has_pending_exception()))) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1460, "assert(" "(((ThreadShadow*)__the_thread__)->has_pending_exception())" ") failed", "expected a pending IMSE here."); ::breakpoint() ; } } while (0); return; } } while (false); // Throws IMSE if not owner. |
| 1461 | |
| 1462 | EventJavaMonitorWait event; |
| 1463 | |
| 1464 | // check for a pending interrupt |
| 1465 | if (interruptible && current->is_interrupted(true) && !HAS_PENDING_EXCEPTION(((ThreadShadow*)__the_thread__)->has_pending_exception())) { |
| 1466 | // post monitor waited event. Note that this is past-tense, we are done waiting. |
| 1467 | if (JvmtiExport::should_post_monitor_waited()) { |
| 1468 | // Note: 'false' parameter is passed here because the |
| 1469 | // wait was not timed out due to thread interrupt. |
| 1470 | JvmtiExport::post_monitor_waited(current, this, false); |
| 1471 | |
| 1472 | // In this short circuit of the monitor wait protocol, the |
| 1473 | // current thread never drops ownership of the monitor and |
| 1474 | // never gets added to the wait queue so the current thread |
| 1475 | // cannot be made the successor. This means that the |
| 1476 | // JVMTI_EVENT_MONITOR_WAITED event handler cannot accidentally |
| 1477 | // consume an unpark() meant for the ParkEvent associated with |
| 1478 | // this ObjectMonitor. |
| 1479 | } |
| 1480 | if (event.should_commit()) { |
| 1481 | post_monitor_wait_event(&event, this, 0, millis, false); |
| 1482 | } |
| 1483 | THROW(vmSymbols::java_lang_InterruptedException()){ Exceptions::_throw_msg(__the_thread__, "/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1483, vmSymbols::java_lang_InterruptedException(), __null); return; }; |
| 1484 | return; |
| 1485 | } |
| 1486 | |
| 1487 | assert(current->_Stalled == 0, "invariant")do { if (!(current->_Stalled == 0)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1487, "assert(" "current->_Stalled == 0" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1488 | current->_Stalled = intptr_t(this); |
| 1489 | current->set_current_waiting_monitor(this); |
| 1490 | |
| 1491 | // create a node to be put into the queue |
| 1492 | // Critically, after we reset() the event but prior to park(), we must check |
| 1493 | // for a pending interrupt. |
| 1494 | ObjectWaiter node(current); |
| 1495 | node.TState = ObjectWaiter::TS_WAIT; |
| 1496 | current->_ParkEvent->reset(); |
| 1497 | OrderAccess::fence(); // ST into Event; membar ; LD interrupted-flag |
| 1498 | |
| 1499 | // Enter the waiting queue, which is a circular doubly linked list in this case |
| 1500 | // but it could be a priority queue or any data structure. |
| 1501 | // _WaitSetLock protects the wait queue. Normally the wait queue is accessed only |
| 1502 | // by the the owner of the monitor *except* in the case where park() |
| 1503 | // returns because of a timeout of interrupt. Contention is exceptionally rare |
| 1504 | // so we use a simple spin-lock instead of a heavier-weight blocking lock. |
| 1505 | |
| 1506 | Thread::SpinAcquire(&_WaitSetLock, "WaitSet - add"); |
| 1507 | AddWaiter(&node); |
| 1508 | Thread::SpinRelease(&_WaitSetLock); |
| 1509 | |
| 1510 | _Responsible = NULL__null; |
| 1511 | |
| 1512 | intx save = _recursions; // record the old recursion count |
| 1513 | _waiters++; // increment the number of waiters |
| 1514 | _recursions = 0; // set the recursion level to be 1 |
| 1515 | exit(current); // exit the monitor |
| 1516 | guarantee(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1516, "guarantee(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1517 | |
| 1518 | // The thread is on the WaitSet list - now park() it. |
| 1519 | // On MP systems it's conceivable that a brief spin before we park |
| 1520 | // could be profitable. |
| 1521 | // |
| 1522 | // TODO-FIXME: change the following logic to a loop of the form |
| 1523 | // while (!timeout && !interrupted && _notified == 0) park() |
| 1524 | |
| 1525 | int ret = OS_OK; |
| 1526 | int WasNotified = 0; |
| 1527 | |
| 1528 | // Need to check interrupt state whilst still _thread_in_vm |
| 1529 | bool interrupted = interruptible && current->is_interrupted(false); |
| 1530 | |
| 1531 | { // State transition wrappers |
| 1532 | OSThread* osthread = current->osthread(); |
| 1533 | OSThreadWaitState osts(osthread, true); |
| 1534 | |
| 1535 | assert(current->thread_state() == _thread_in_vm, "invariant")do { if (!(current->thread_state() == _thread_in_vm)) { (* g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1535, "assert(" "current->thread_state() == _thread_in_vm" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1536 | |
| 1537 | { |
| 1538 | ClearSuccOnSuspend csos(this); |
| 1539 | ThreadBlockInVMPreprocess<ClearSuccOnSuspend> tbivs(current, csos, true /* allow_suspend */); |
| 1540 | if (interrupted || HAS_PENDING_EXCEPTION(((ThreadShadow*)__the_thread__)->has_pending_exception())) { |
| 1541 | // Intentionally empty |
| 1542 | } else if (node._notified == 0) { |
| 1543 | if (millis <= 0) { |
| 1544 | current->_ParkEvent->park(); |
| 1545 | } else { |
| 1546 | ret = current->_ParkEvent->park(millis); |
| 1547 | } |
| 1548 | } |
| 1549 | } |
| 1550 | |
| 1551 | // Node may be on the WaitSet, the EntryList (or cxq), or in transition |
| 1552 | // from the WaitSet to the EntryList. |
| 1553 | // See if we need to remove Node from the WaitSet. |
| 1554 | // We use double-checked locking to avoid grabbing _WaitSetLock |
| 1555 | // if the thread is not on the wait queue. |
| 1556 | // |
| 1557 | // Note that we don't need a fence before the fetch of TState. |
| 1558 | // In the worst case we'll fetch a old-stale value of TS_WAIT previously |
| 1559 | // written by the is thread. (perhaps the fetch might even be satisfied |
| 1560 | // by a look-aside into the processor's own store buffer, although given |
| 1561 | // the length of the code path between the prior ST and this load that's |
| 1562 | // highly unlikely). If the following LD fetches a stale TS_WAIT value |
| 1563 | // then we'll acquire the lock and then re-fetch a fresh TState value. |
| 1564 | // That is, we fail toward safety. |
| 1565 | |
| 1566 | if (node.TState == ObjectWaiter::TS_WAIT) { |
| 1567 | Thread::SpinAcquire(&_WaitSetLock, "WaitSet - unlink"); |
| 1568 | if (node.TState == ObjectWaiter::TS_WAIT) { |
| 1569 | DequeueSpecificWaiter(&node); // unlink from WaitSet |
| 1570 | assert(node._notified == 0, "invariant")do { if (!(node._notified == 0)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1570, "assert(" "node._notified == 0" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1571 | node.TState = ObjectWaiter::TS_RUN; |
| 1572 | } |
| 1573 | Thread::SpinRelease(&_WaitSetLock); |
| 1574 | } |
| 1575 | |
| 1576 | // The thread is now either on off-list (TS_RUN), |
| 1577 | // on the EntryList (TS_ENTER), or on the cxq (TS_CXQ). |
| 1578 | // The Node's TState variable is stable from the perspective of this thread. |
| 1579 | // No other threads will asynchronously modify TState. |
| 1580 | guarantee(node.TState != ObjectWaiter::TS_WAIT, "invariant")do { if (!(node.TState != ObjectWaiter::TS_WAIT)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1580, "guarantee(" "node.TState != ObjectWaiter::TS_WAIT" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1581 | OrderAccess::loadload(); |
| 1582 | if (_succ == current) _succ = NULL__null; |
| 1583 | WasNotified = node._notified; |
| 1584 | |
| 1585 | // Reentry phase -- reacquire the monitor. |
| 1586 | // re-enter contended monitor after object.wait(). |
| 1587 | // retain OBJECT_WAIT state until re-enter successfully completes |
| 1588 | // Thread state is thread_in_vm and oop access is again safe, |
| 1589 | // although the raw address of the object may have changed. |
| 1590 | // (Don't cache naked oops over safepoints, of course). |
| 1591 | |
| 1592 | // post monitor waited event. Note that this is past-tense, we are done waiting. |
| 1593 | if (JvmtiExport::should_post_monitor_waited()) { |
| 1594 | JvmtiExport::post_monitor_waited(current, this, ret == OS_TIMEOUT); |
| 1595 | |
| 1596 | if (node._notified != 0 && _succ == current) { |
| 1597 | // In this part of the monitor wait-notify-reenter protocol it |
| 1598 | // is possible (and normal) for another thread to do a fastpath |
| 1599 | // monitor enter-exit while this thread is still trying to get |
| 1600 | // to the reenter portion of the protocol. |
| 1601 | // |
| 1602 | // The ObjectMonitor was notified and the current thread is |
| 1603 | // the successor which also means that an unpark() has already |
| 1604 | // been done. The JVMTI_EVENT_MONITOR_WAITED event handler can |
| 1605 | // consume the unpark() that was done when the successor was |
| 1606 | // set because the same ParkEvent is shared between Java |
| 1607 | // monitors and JVM/TI RawMonitors (for now). |
| 1608 | // |
| 1609 | // We redo the unpark() to ensure forward progress, i.e., we |
| 1610 | // don't want all pending threads hanging (parked) with none |
| 1611 | // entering the unlocked monitor. |
| 1612 | node._event->unpark(); |
| 1613 | } |
| 1614 | } |
| 1615 | |
| 1616 | if (event.should_commit()) { |
| 1617 | post_monitor_wait_event(&event, this, node._notifier_tid, millis, ret == OS_TIMEOUT); |
| 1618 | } |
| 1619 | |
| 1620 | OrderAccess::fence(); |
| 1621 | |
| 1622 | assert(current->_Stalled != 0, "invariant")do { if (!(current->_Stalled != 0)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1622, "assert(" "current->_Stalled != 0" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1623 | current->_Stalled = 0; |
| 1624 | |
| 1625 | assert(owner_raw() != current, "invariant")do { if (!(owner_raw() != current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1625, "assert(" "owner_raw() != current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1626 | ObjectWaiter::TStates v = node.TState; |
| 1627 | if (v == ObjectWaiter::TS_RUN) { |
| 1628 | enter(current); |
| 1629 | } else { |
| 1630 | guarantee(v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ, "invariant")do { if (!(v == ObjectWaiter::TS_ENTER || v == ObjectWaiter:: TS_CXQ)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1630, "guarantee(" "v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1631 | ReenterI(current, &node); |
| 1632 | node.wait_reenter_end(this); |
| 1633 | } |
| 1634 | |
| 1635 | // current has reacquired the lock. |
| 1636 | // Lifecycle - the node representing current must not appear on any queues. |
| 1637 | // Node is about to go out-of-scope, but even if it were immortal we wouldn't |
| 1638 | // want residual elements associated with this thread left on any lists. |
| 1639 | guarantee(node.TState == ObjectWaiter::TS_RUN, "invariant")do { if (!(node.TState == ObjectWaiter::TS_RUN)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1639, "guarantee(" "node.TState == ObjectWaiter::TS_RUN" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1640 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1640, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1641 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1641, "assert(" "_succ != current" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1642 | } // OSThreadWaitState() |
| 1643 | |
| 1644 | current->set_current_waiting_monitor(NULL__null); |
| 1645 | |
| 1646 | guarantee(_recursions == 0, "invariant")do { if (!(_recursions == 0)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1646, "guarantee(" "_recursions == 0" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1647 | _recursions = save // restore the old recursion count |
| 1648 | + JvmtiDeferredUpdates::get_and_reset_relock_count_after_wait(current); // increased by the deferred relock count |
| 1649 | _waiters--; // decrement the number of waiters |
| 1650 | |
| 1651 | // Verify a few postconditions |
| 1652 | assert(owner_raw() == current, "invariant")do { if (!(owner_raw() == current)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1652, "assert(" "owner_raw() == current" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1653 | assert(_succ != current, "invariant")do { if (!(_succ != current)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1653, "assert(" "_succ != current" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1654 | assert(object()->mark() == markWord::encode(this), "invariant")do { if (!(object()->mark() == markWord::encode(this))) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1654, "assert(" "object()->mark() == markWord::encode(this)" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1655 | |
| 1656 | // check if the notification happened |
| 1657 | if (!WasNotified) { |
| 1658 | // no, it could be timeout or Thread.interrupt() or both |
| 1659 | // check for interrupt event, otherwise it is timeout |
| 1660 | if (interruptible && current->is_interrupted(true) && !HAS_PENDING_EXCEPTION(((ThreadShadow*)__the_thread__)->has_pending_exception())) { |
| 1661 | THROW(vmSymbols::java_lang_InterruptedException()){ Exceptions::_throw_msg(__the_thread__, "/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1661, vmSymbols::java_lang_InterruptedException(), __null); return; }; |
| 1662 | } |
| 1663 | } |
| 1664 | |
| 1665 | // NOTE: Spurious wake up will be consider as timeout. |
| 1666 | // Monitor notify has precedence over thread interrupt. |
| 1667 | } |
| 1668 | |
| 1669 | |
| 1670 | // Consider: |
| 1671 | // If the lock is cool (cxq == null && succ == null) and we're on an MP system |
| 1672 | // then instead of transferring a thread from the WaitSet to the EntryList |
| 1673 | // we might just dequeue a thread from the WaitSet and directly unpark() it. |
| 1674 | |
| 1675 | void ObjectMonitor::INotify(JavaThread* current) { |
| 1676 | Thread::SpinAcquire(&_WaitSetLock, "WaitSet - notify"); |
| 1677 | ObjectWaiter* iterator = DequeueWaiter(); |
| 1678 | if (iterator != NULL__null) { |
| 1679 | guarantee(iterator->TState == ObjectWaiter::TS_WAIT, "invariant")do { if (!(iterator->TState == ObjectWaiter::TS_WAIT)) { ( *g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1679, "guarantee(" "iterator->TState == ObjectWaiter::TS_WAIT" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1680 | guarantee(iterator->_notified == 0, "invariant")do { if (!(iterator->_notified == 0)) { (*g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1680, "guarantee(" "iterator->_notified == 0" ") failed" , "invariant"); ::breakpoint(); } } while (0); |
| 1681 | // Disposition - what might we do with iterator ? |
| 1682 | // a. add it directly to the EntryList - either tail (policy == 1) |
| 1683 | // or head (policy == 0). |
| 1684 | // b. push it onto the front of the _cxq (policy == 2). |
| 1685 | // For now we use (b). |
| 1686 | |
| 1687 | iterator->TState = ObjectWaiter::TS_ENTER; |
| 1688 | |
| 1689 | iterator->_notified = 1; |
| 1690 | iterator->_notifier_tid = JFR_THREAD_ID(current)((current)->jfr_thread_local()->thread_id()); |
| 1691 | |
| 1692 | ObjectWaiter* list = _EntryList; |
| 1693 | if (list != NULL__null) { |
| 1694 | assert(list->_prev == NULL, "invariant")do { if (!(list->_prev == __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1694, "assert(" "list->_prev == __null" ") failed", "invariant" ); ::breakpoint(); } } while (0); |
| 1695 | assert(list->TState == ObjectWaiter::TS_ENTER, "invariant")do { if (!(list->TState == ObjectWaiter::TS_ENTER)) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1695, "assert(" "list->TState == ObjectWaiter::TS_ENTER" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 1696 | assert(list != iterator, "invariant")do { if (!(list != iterator)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1696, "assert(" "list != iterator" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 1697 | } |
| 1698 | |
| 1699 | // prepend to cxq |
| 1700 | if (list == NULL__null) { |
| 1701 | iterator->_next = iterator->_prev = NULL__null; |
| 1702 | _EntryList = iterator; |
| 1703 | } else { |
| 1704 | iterator->TState = ObjectWaiter::TS_CXQ; |
| 1705 | for (;;) { |
| 1706 | ObjectWaiter* front = _cxq; |
| 1707 | iterator->_next = front; |
| 1708 | if (Atomic::cmpxchg(&_cxq, front, iterator) == front) { |
| 1709 | break; |
| 1710 | } |
| 1711 | } |
| 1712 | } |
| 1713 | |
| 1714 | // _WaitSetLock protects the wait queue, not the EntryList. We could |
| 1715 | // move the add-to-EntryList operation, above, outside the critical section |
| 1716 | // protected by _WaitSetLock. In practice that's not useful. With the |
| 1717 | // exception of wait() timeouts and interrupts the monitor owner |
| 1718 | // is the only thread that grabs _WaitSetLock. There's almost no contention |
| 1719 | // on _WaitSetLock so it's not profitable to reduce the length of the |
| 1720 | // critical section. |
| 1721 | |
| 1722 | iterator->wait_reenter_begin(this); |
| 1723 | } |
| 1724 | Thread::SpinRelease(&_WaitSetLock); |
| 1725 | } |
| 1726 | |
| 1727 | // Consider: a not-uncommon synchronization bug is to use notify() when |
| 1728 | // notifyAll() is more appropriate, potentially resulting in stranded |
| 1729 | // threads; this is one example of a lost wakeup. A useful diagnostic |
| 1730 | // option is to force all notify() operations to behave as notifyAll(). |
| 1731 | // |
| 1732 | // Note: We can also detect many such problems with a "minimum wait". |
| 1733 | // When the "minimum wait" is set to a small non-zero timeout value |
| 1734 | // and the program does not hang whereas it did absent "minimum wait", |
| 1735 | // that suggests a lost wakeup bug. |
| 1736 | |
| 1737 | void ObjectMonitor::notify(TRAPSJavaThread* __the_thread__) { |
| 1738 | JavaThread* current = THREAD__the_thread__; |
| 1739 | CHECK_OWNER()do { if (!check_owner(__the_thread__)) { do { if (!((((ThreadShadow *)__the_thread__)->has_pending_exception()))) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1739, "assert(" "(((ThreadShadow*)__the_thread__)->has_pending_exception())" ") failed", "expected a pending IMSE here."); ::breakpoint() ; } } while (0); return; } } while (false); // Throws IMSE if not owner. |
| 1740 | if (_WaitSet == NULL__null) { |
| 1741 | return; |
| 1742 | } |
| 1743 | DTRACE_MONITOR_PROBE(notify, this, object(), current){;}; |
| 1744 | INotify(current); |
| 1745 | OM_PERFDATA_OP(Notifications, inc(1))do { if (ObjectMonitor::_sync_Notifications != __null && PerfDataManager::has_PerfData()) { ObjectMonitor::_sync_Notifications ->inc(1); } } while (0); |
| 1746 | } |
| 1747 | |
| 1748 | |
| 1749 | // The current implementation of notifyAll() transfers the waiters one-at-a-time |
| 1750 | // from the waitset to the EntryList. This could be done more efficiently with a |
| 1751 | // single bulk transfer but in practice it's not time-critical. Beware too, |
| 1752 | // that in prepend-mode we invert the order of the waiters. Let's say that the |
| 1753 | // waitset is "ABCD" and the EntryList is "XYZ". After a notifyAll() in prepend |
| 1754 | // mode the waitset will be empty and the EntryList will be "DCBAXYZ". |
| 1755 | |
| 1756 | void ObjectMonitor::notifyAll(TRAPSJavaThread* __the_thread__) { |
| 1757 | JavaThread* current = THREAD__the_thread__; |
| 1758 | CHECK_OWNER()do { if (!check_owner(__the_thread__)) { do { if (!((((ThreadShadow *)__the_thread__)->has_pending_exception()))) { (*g_assert_poison ) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 1758, "assert(" "(((ThreadShadow*)__the_thread__)->has_pending_exception())" ") failed", "expected a pending IMSE here."); ::breakpoint() ; } } while (0); return; } } while (false); // Throws IMSE if not owner. |
| 1759 | if (_WaitSet == NULL__null) { |
| 1760 | return; |
| 1761 | } |
| 1762 | |
| 1763 | DTRACE_MONITOR_PROBE(notifyAll, this, object(), current){;}; |
| 1764 | int tally = 0; |
| 1765 | while (_WaitSet != NULL__null) { |
| 1766 | tally++; |
| 1767 | INotify(current); |
| 1768 | } |
| 1769 | |
| 1770 | OM_PERFDATA_OP(Notifications, inc(tally))do { if (ObjectMonitor::_sync_Notifications != __null && PerfDataManager::has_PerfData()) { ObjectMonitor::_sync_Notifications ->inc(tally); } } while (0); |
| 1771 | } |
| 1772 | |
| 1773 | // ----------------------------------------------------------------------------- |
| 1774 | // Adaptive Spinning Support |
| 1775 | // |
| 1776 | // Adaptive spin-then-block - rational spinning |
| 1777 | // |
| 1778 | // Note that we spin "globally" on _owner with a classic SMP-polite TATAS |
| 1779 | // algorithm. On high order SMP systems it would be better to start with |
| 1780 | // a brief global spin and then revert to spinning locally. In the spirit of MCS/CLH, |
| 1781 | // a contending thread could enqueue itself on the cxq and then spin locally |
| 1782 | // on a thread-specific variable such as its ParkEvent._Event flag. |
| 1783 | // That's left as an exercise for the reader. Note that global spinning is |
| 1784 | // not problematic on Niagara, as the L2 cache serves the interconnect and |
| 1785 | // has both low latency and massive bandwidth. |
| 1786 | // |
| 1787 | // Broadly, we can fix the spin frequency -- that is, the % of contended lock |
| 1788 | // acquisition attempts where we opt to spin -- at 100% and vary the spin count |
| 1789 | // (duration) or we can fix the count at approximately the duration of |
| 1790 | // a context switch and vary the frequency. Of course we could also |
| 1791 | // vary both satisfying K == Frequency * Duration, where K is adaptive by monitor. |
| 1792 | // For a description of 'Adaptive spin-then-block mutual exclusion in |
| 1793 | // multi-threaded processing,' see U.S. Pat. No. 8046758. |
| 1794 | // |
| 1795 | // This implementation varies the duration "D", where D varies with |
| 1796 | // the success rate of recent spin attempts. (D is capped at approximately |
| 1797 | // length of a round-trip context switch). The success rate for recent |
| 1798 | // spin attempts is a good predictor of the success rate of future spin |
| 1799 | // attempts. The mechanism adapts automatically to varying critical |
| 1800 | // section length (lock modality), system load and degree of parallelism. |
| 1801 | // D is maintained per-monitor in _SpinDuration and is initialized |
| 1802 | // optimistically. Spin frequency is fixed at 100%. |
| 1803 | // |
| 1804 | // Note that _SpinDuration is volatile, but we update it without locks |
| 1805 | // or atomics. The code is designed so that _SpinDuration stays within |
| 1806 | // a reasonable range even in the presence of races. The arithmetic |
| 1807 | // operations on _SpinDuration are closed over the domain of legal values, |
| 1808 | // so at worst a race will install and older but still legal value. |
| 1809 | // At the very worst this introduces some apparent non-determinism. |
| 1810 | // We might spin when we shouldn't or vice-versa, but since the spin |
| 1811 | // count are relatively short, even in the worst case, the effect is harmless. |
| 1812 | // |
| 1813 | // Care must be taken that a low "D" value does not become an |
| 1814 | // an absorbing state. Transient spinning failures -- when spinning |
| 1815 | // is overall profitable -- should not cause the system to converge |
| 1816 | // on low "D" values. We want spinning to be stable and predictable |
| 1817 | // and fairly responsive to change and at the same time we don't want |
| 1818 | // it to oscillate, become metastable, be "too" non-deterministic, |
| 1819 | // or converge on or enter undesirable stable absorbing states. |
| 1820 | // |
| 1821 | // We implement a feedback-based control system -- using past behavior |
| 1822 | // to predict future behavior. We face two issues: (a) if the |
| 1823 | // input signal is random then the spin predictor won't provide optimal |
| 1824 | // results, and (b) if the signal frequency is too high then the control |
| 1825 | // system, which has some natural response lag, will "chase" the signal. |
| 1826 | // (b) can arise from multimodal lock hold times. Transient preemption |
| 1827 | // can also result in apparent bimodal lock hold times. |
| 1828 | // Although sub-optimal, neither condition is particularly harmful, as |
| 1829 | // in the worst-case we'll spin when we shouldn't or vice-versa. |
| 1830 | // The maximum spin duration is rather short so the failure modes aren't bad. |
| 1831 | // To be conservative, I've tuned the gain in system to bias toward |
| 1832 | // _not spinning. Relatedly, the system can sometimes enter a mode where it |
| 1833 | // "rings" or oscillates between spinning and not spinning. This happens |
| 1834 | // when spinning is just on the cusp of profitability, however, so the |
| 1835 | // situation is not dire. The state is benign -- there's no need to add |
| 1836 | // hysteresis control to damp the transition rate between spinning and |
| 1837 | // not spinning. |
| 1838 | |
| 1839 | // Spinning: Fixed frequency (100%), vary duration |
| 1840 | int ObjectMonitor::TrySpin(JavaThread* current) { |
| 1841 | // Dumb, brutal spin. Good for comparative measurements against adaptive spinning. |
| 1842 | int ctr = Knob_FixedSpin; |
| 1843 | if (ctr != 0) { |
| 1844 | while (--ctr >= 0) { |
| 1845 | if (TryLock(current) > 0) return 1; |
| 1846 | SpinPause(); |
| 1847 | } |
| 1848 | return 0; |
| 1849 | } |
| 1850 | |
| 1851 | for (ctr = Knob_PreSpin + 1; --ctr >= 0;) { |
| 1852 | if (TryLock(current) > 0) { |
| 1853 | // Increase _SpinDuration ... |
| 1854 | // Note that we don't clamp SpinDuration precisely at SpinLimit. |
| 1855 | // Raising _SpurDuration to the poverty line is key. |
| 1856 | int x = _SpinDuration; |
| 1857 | if (x < Knob_SpinLimit) { |
| 1858 | if (x < Knob_Poverty) x = Knob_Poverty; |
| 1859 | _SpinDuration = x + Knob_BonusB; |
| 1860 | } |
| 1861 | return 1; |
| 1862 | } |
| 1863 | SpinPause(); |
| 1864 | } |
| 1865 | |
| 1866 | // Admission control - verify preconditions for spinning |
| 1867 | // |
| 1868 | // We always spin a little bit, just to prevent _SpinDuration == 0 from |
| 1869 | // becoming an absorbing state. Put another way, we spin briefly to |
| 1870 | // sample, just in case the system load, parallelism, contention, or lock |
| 1871 | // modality changed. |
| 1872 | // |
| 1873 | // Consider the following alternative: |
| 1874 | // Periodically set _SpinDuration = _SpinLimit and try a long/full |
| 1875 | // spin attempt. "Periodically" might mean after a tally of |
| 1876 | // the # of failed spin attempts (or iterations) reaches some threshold. |
| 1877 | // This takes us into the realm of 1-out-of-N spinning, where we |
| 1878 | // hold the duration constant but vary the frequency. |
| 1879 | |
| 1880 | ctr = _SpinDuration; |
| 1881 | if (ctr <= 0) return 0; |
| 1882 | |
| 1883 | if (NotRunnable(current, (JavaThread*) owner_raw())) { |
| 1884 | return 0; |
| 1885 | } |
| 1886 | |
| 1887 | // We're good to spin ... spin ingress. |
| 1888 | // CONSIDER: use Prefetch::write() to avoid RTS->RTO upgrades |
| 1889 | // when preparing to LD...CAS _owner, etc and the CAS is likely |
| 1890 | // to succeed. |
| 1891 | if (_succ == NULL__null) { |
| 1892 | _succ = current; |
| 1893 | } |
| 1894 | Thread* prv = NULL__null; |
| 1895 | |
| 1896 | // There are three ways to exit the following loop: |
| 1897 | // 1. A successful spin where this thread has acquired the lock. |
| 1898 | // 2. Spin failure with prejudice |
| 1899 | // 3. Spin failure without prejudice |
| 1900 | |
| 1901 | while (--ctr >= 0) { |
| 1902 | |
| 1903 | // Periodic polling -- Check for pending GC |
| 1904 | // Threads may spin while they're unsafe. |
| 1905 | // We don't want spinning threads to delay the JVM from reaching |
| 1906 | // a stop-the-world safepoint or to steal cycles from GC. |
| 1907 | // If we detect a pending safepoint we abort in order that |
| 1908 | // (a) this thread, if unsafe, doesn't delay the safepoint, and (b) |
| 1909 | // this thread, if safe, doesn't steal cycles from GC. |
| 1910 | // This is in keeping with the "no loitering in runtime" rule. |
| 1911 | // We periodically check to see if there's a safepoint pending. |
| 1912 | if ((ctr & 0xFF) == 0) { |
| 1913 | if (SafepointMechanism::should_process(current)) { |
| 1914 | goto Abort; // abrupt spin egress |
| 1915 | } |
| 1916 | SpinPause(); |
| 1917 | } |
| 1918 | |
| 1919 | // Probe _owner with TATAS |
| 1920 | // If this thread observes the monitor transition or flicker |
| 1921 | // from locked to unlocked to locked, then the odds that this |
| 1922 | // thread will acquire the lock in this spin attempt go down |
| 1923 | // considerably. The same argument applies if the CAS fails |
| 1924 | // or if we observe _owner change from one non-null value to |
| 1925 | // another non-null value. In such cases we might abort |
| 1926 | // the spin without prejudice or apply a "penalty" to the |
| 1927 | // spin count-down variable "ctr", reducing it by 100, say. |
| 1928 | |
| 1929 | JavaThread* ox = (JavaThread*) owner_raw(); |
| 1930 | if (ox == NULL__null) { |
| 1931 | ox = (JavaThread*)try_set_owner_from(NULL__null, current); |
| 1932 | if (ox == NULL__null) { |
| 1933 | // The CAS succeeded -- this thread acquired ownership |
| 1934 | // Take care of some bookkeeping to exit spin state. |
| 1935 | if (_succ == current) { |
| 1936 | _succ = NULL__null; |
| 1937 | } |
| 1938 | |
| 1939 | // Increase _SpinDuration : |
| 1940 | // The spin was successful (profitable) so we tend toward |
| 1941 | // longer spin attempts in the future. |
| 1942 | // CONSIDER: factor "ctr" into the _SpinDuration adjustment. |
| 1943 | // If we acquired the lock early in the spin cycle it |
| 1944 | // makes sense to increase _SpinDuration proportionally. |
| 1945 | // Note that we don't clamp SpinDuration precisely at SpinLimit. |
| 1946 | int x = _SpinDuration; |
| 1947 | if (x < Knob_SpinLimit) { |
| 1948 | if (x < Knob_Poverty) x = Knob_Poverty; |
| 1949 | _SpinDuration = x + Knob_Bonus; |
| 1950 | } |
| 1951 | return 1; |
| 1952 | } |
| 1953 | |
| 1954 | // The CAS failed ... we can take any of the following actions: |
| 1955 | // * penalize: ctr -= CASPenalty |
| 1956 | // * exit spin with prejudice -- goto Abort; |
| 1957 | // * exit spin without prejudice. |
| 1958 | // * Since CAS is high-latency, retry again immediately. |
| 1959 | prv = ox; |
Value stored to 'prv' is never read | |
| 1960 | goto Abort; |
| 1961 | } |
| 1962 | |
| 1963 | // Did lock ownership change hands ? |
| 1964 | if (ox != prv && prv != NULL__null) { |
| 1965 | goto Abort; |
| 1966 | } |
| 1967 | prv = ox; |
| 1968 | |
| 1969 | // Abort the spin if the owner is not executing. |
| 1970 | // The owner must be executing in order to drop the lock. |
| 1971 | // Spinning while the owner is OFFPROC is idiocy. |
| 1972 | // Consider: ctr -= RunnablePenalty ; |
| 1973 | if (NotRunnable(current, ox)) { |
| 1974 | goto Abort; |
| 1975 | } |
| 1976 | if (_succ == NULL__null) { |
| 1977 | _succ = current; |
| 1978 | } |
| 1979 | } |
| 1980 | |
| 1981 | // Spin failed with prejudice -- reduce _SpinDuration. |
| 1982 | // TODO: Use an AIMD-like policy to adjust _SpinDuration. |
| 1983 | // AIMD is globally stable. |
| 1984 | { |
| 1985 | int x = _SpinDuration; |
| 1986 | if (x > 0) { |
| 1987 | // Consider an AIMD scheme like: x -= (x >> 3) + 100 |
| 1988 | // This is globally sample and tends to damp the response. |
| 1989 | x -= Knob_Penalty; |
| 1990 | if (x < 0) x = 0; |
| 1991 | _SpinDuration = x; |
| 1992 | } |
| 1993 | } |
| 1994 | |
| 1995 | Abort: |
| 1996 | if (_succ == current) { |
| 1997 | _succ = NULL__null; |
| 1998 | // Invariant: after setting succ=null a contending thread |
| 1999 | // must recheck-retry _owner before parking. This usually happens |
| 2000 | // in the normal usage of TrySpin(), but it's safest |
| 2001 | // to make TrySpin() as foolproof as possible. |
| 2002 | OrderAccess::fence(); |
| 2003 | if (TryLock(current) > 0) return 1; |
| 2004 | } |
| 2005 | return 0; |
| 2006 | } |
| 2007 | |
| 2008 | // NotRunnable() -- informed spinning |
| 2009 | // |
| 2010 | // Don't bother spinning if the owner is not eligible to drop the lock. |
| 2011 | // Spin only if the owner thread is _thread_in_Java or _thread_in_vm. |
| 2012 | // The thread must be runnable in order to drop the lock in timely fashion. |
| 2013 | // If the _owner is not runnable then spinning will not likely be |
| 2014 | // successful (profitable). |
| 2015 | // |
| 2016 | // Beware -- the thread referenced by _owner could have died |
| 2017 | // so a simply fetch from _owner->_thread_state might trap. |
| 2018 | // Instead, we use SafeFetchXX() to safely LD _owner->_thread_state. |
| 2019 | // Because of the lifecycle issues, the _thread_state values |
| 2020 | // observed by NotRunnable() might be garbage. NotRunnable must |
| 2021 | // tolerate this and consider the observed _thread_state value |
| 2022 | // as advisory. |
| 2023 | // |
| 2024 | // Beware too, that _owner is sometimes a BasicLock address and sometimes |
| 2025 | // a thread pointer. |
| 2026 | // Alternately, we might tag the type (thread pointer vs basiclock pointer) |
| 2027 | // with the LSB of _owner. Another option would be to probabilistically probe |
| 2028 | // the putative _owner->TypeTag value. |
| 2029 | // |
| 2030 | // Checking _thread_state isn't perfect. Even if the thread is |
| 2031 | // in_java it might be blocked on a page-fault or have been preempted |
| 2032 | // and sitting on a ready/dispatch queue. |
| 2033 | // |
| 2034 | // The return value from NotRunnable() is *advisory* -- the |
| 2035 | // result is based on sampling and is not necessarily coherent. |
| 2036 | // The caller must tolerate false-negative and false-positive errors. |
| 2037 | // Spinning, in general, is probabilistic anyway. |
| 2038 | |
| 2039 | |
| 2040 | int ObjectMonitor::NotRunnable(JavaThread* current, JavaThread* ox) { |
| 2041 | // Check ox->TypeTag == 2BAD. |
| 2042 | if (ox == NULL__null) return 0; |
| 2043 | |
| 2044 | // Avoid transitive spinning ... |
| 2045 | // Say T1 spins or blocks trying to acquire L. T1._Stalled is set to L. |
| 2046 | // Immediately after T1 acquires L it's possible that T2, also |
| 2047 | // spinning on L, will see L.Owner=T1 and T1._Stalled=L. |
| 2048 | // This occurs transiently after T1 acquired L but before |
| 2049 | // T1 managed to clear T1.Stalled. T2 does not need to abort |
| 2050 | // its spin in this circumstance. |
| 2051 | intptr_t BlockedOn = SafeFetchN((intptr_t *) &ox->_Stalled, intptr_t(1)); |
| 2052 | |
| 2053 | if (BlockedOn == 1) return 1; |
| 2054 | if (BlockedOn != 0) { |
| 2055 | return BlockedOn != intptr_t(this) && owner_raw() == ox; |
| 2056 | } |
| 2057 | |
| 2058 | assert(sizeof(ox->_thread_state == sizeof(int)), "invariant")do { if (!(sizeof(ox->_thread_state == sizeof(int)))) { (* g_assert_poison) = 'X';; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2058, "assert(" "sizeof(ox->_thread_state == sizeof(int))" ") failed", "invariant"); ::breakpoint(); } } while (0); |
| 2059 | int jst = SafeFetch32((int *) &ox->_thread_state, -1);; |
| 2060 | // consider also: jst != _thread_in_Java -- but that's overspecific. |
| 2061 | return jst == _thread_blocked || jst == _thread_in_native; |
| 2062 | } |
| 2063 | |
| 2064 | |
| 2065 | // ----------------------------------------------------------------------------- |
| 2066 | // WaitSet management ... |
| 2067 | |
| 2068 | ObjectWaiter::ObjectWaiter(JavaThread* current) { |
| 2069 | _next = NULL__null; |
| 2070 | _prev = NULL__null; |
| 2071 | _notified = 0; |
| 2072 | _notifier_tid = 0; |
| 2073 | TState = TS_RUN; |
| 2074 | _thread = current; |
| 2075 | _event = _thread->_ParkEvent; |
| 2076 | _active = false; |
| 2077 | assert(_event != NULL, "invariant")do { if (!(_event != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2077, "assert(" "_event != __null" ") failed", "invariant") ; ::breakpoint(); } } while (0); |
| 2078 | } |
| 2079 | |
| 2080 | void ObjectWaiter::wait_reenter_begin(ObjectMonitor * const mon) { |
| 2081 | _active = JavaThreadBlockedOnMonitorEnterState::wait_reenter_begin(_thread, mon); |
| 2082 | } |
| 2083 | |
| 2084 | void ObjectWaiter::wait_reenter_end(ObjectMonitor * const mon) { |
| 2085 | JavaThreadBlockedOnMonitorEnterState::wait_reenter_end(_thread, _active); |
| 2086 | } |
| 2087 | |
| 2088 | inline void ObjectMonitor::AddWaiter(ObjectWaiter* node) { |
| 2089 | assert(node != NULL, "should not add NULL node")do { if (!(node != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2089, "assert(" "node != __null" ") failed", "should not add NULL node" ); ::breakpoint(); } } while (0); |
| 2090 | assert(node->_prev == NULL, "node already in list")do { if (!(node->_prev == __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2090, "assert(" "node->_prev == __null" ") failed", "node already in list" ); ::breakpoint(); } } while (0); |
| 2091 | assert(node->_next == NULL, "node already in list")do { if (!(node->_next == __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2091, "assert(" "node->_next == __null" ") failed", "node already in list" ); ::breakpoint(); } } while (0); |
| 2092 | // put node at end of queue (circular doubly linked list) |
| 2093 | if (_WaitSet == NULL__null) { |
| 2094 | _WaitSet = node; |
| 2095 | node->_prev = node; |
| 2096 | node->_next = node; |
| 2097 | } else { |
| 2098 | ObjectWaiter* head = _WaitSet; |
| 2099 | ObjectWaiter* tail = head->_prev; |
| 2100 | assert(tail->_next == head, "invariant check")do { if (!(tail->_next == head)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2100, "assert(" "tail->_next == head" ") failed", "invariant check" ); ::breakpoint(); } } while (0); |
| 2101 | tail->_next = node; |
| 2102 | head->_prev = node; |
| 2103 | node->_next = head; |
| 2104 | node->_prev = tail; |
| 2105 | } |
| 2106 | } |
| 2107 | |
| 2108 | inline ObjectWaiter* ObjectMonitor::DequeueWaiter() { |
| 2109 | // dequeue the very first waiter |
| 2110 | ObjectWaiter* waiter = _WaitSet; |
| 2111 | if (waiter) { |
| 2112 | DequeueSpecificWaiter(waiter); |
| 2113 | } |
| 2114 | return waiter; |
| 2115 | } |
| 2116 | |
| 2117 | inline void ObjectMonitor::DequeueSpecificWaiter(ObjectWaiter* node) { |
| 2118 | assert(node != NULL, "should not dequeue NULL node")do { if (!(node != __null)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2118, "assert(" "node != __null" ") failed", "should not dequeue NULL node" ); ::breakpoint(); } } while (0); |
| 2119 | assert(node->_prev != NULL, "node already removed from list")do { if (!(node->_prev != __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2119, "assert(" "node->_prev != __null" ") failed", "node already removed from list" ); ::breakpoint(); } } while (0); |
| 2120 | assert(node->_next != NULL, "node already removed from list")do { if (!(node->_next != __null)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2120, "assert(" "node->_next != __null" ") failed", "node already removed from list" ); ::breakpoint(); } } while (0); |
| 2121 | // when the waiter has woken up because of interrupt, |
| 2122 | // timeout or other spurious wake-up, dequeue the |
| 2123 | // waiter from waiting list |
| 2124 | ObjectWaiter* next = node->_next; |
| 2125 | if (next == node) { |
| 2126 | assert(node->_prev == node, "invariant check")do { if (!(node->_prev == node)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2126, "assert(" "node->_prev == node" ") failed", "invariant check" ); ::breakpoint(); } } while (0); |
| 2127 | _WaitSet = NULL__null; |
| 2128 | } else { |
| 2129 | ObjectWaiter* prev = node->_prev; |
| 2130 | assert(prev->_next == node, "invariant check")do { if (!(prev->_next == node)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2130, "assert(" "prev->_next == node" ") failed", "invariant check" ); ::breakpoint(); } } while (0); |
| 2131 | assert(next->_prev == node, "invariant check")do { if (!(next->_prev == node)) { (*g_assert_poison) = 'X' ;; report_vm_error("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2131, "assert(" "next->_prev == node" ") failed", "invariant check" ); ::breakpoint(); } } while (0); |
| 2132 | next->_prev = prev; |
| 2133 | prev->_next = next; |
| 2134 | if (_WaitSet == node) { |
| 2135 | _WaitSet = next; |
| 2136 | } |
| 2137 | } |
| 2138 | node->_next = NULL__null; |
| 2139 | node->_prev = NULL__null; |
| 2140 | } |
| 2141 | |
| 2142 | // ----------------------------------------------------------------------------- |
| 2143 | // PerfData support |
| 2144 | PerfCounter * ObjectMonitor::_sync_ContendedLockAttempts = NULL__null; |
| 2145 | PerfCounter * ObjectMonitor::_sync_FutileWakeups = NULL__null; |
| 2146 | PerfCounter * ObjectMonitor::_sync_Parks = NULL__null; |
| 2147 | PerfCounter * ObjectMonitor::_sync_Notifications = NULL__null; |
| 2148 | PerfCounter * ObjectMonitor::_sync_Inflations = NULL__null; |
| 2149 | PerfCounter * ObjectMonitor::_sync_Deflations = NULL__null; |
| 2150 | PerfLongVariable * ObjectMonitor::_sync_MonExtant = NULL__null; |
| 2151 | |
| 2152 | // One-shot global initialization for the sync subsystem. |
| 2153 | // We could also defer initialization and initialize on-demand |
| 2154 | // the first time we call ObjectSynchronizer::inflate(). |
| 2155 | // Initialization would be protected - like so many things - by |
| 2156 | // the MonitorCache_lock. |
| 2157 | |
| 2158 | void ObjectMonitor::Initialize() { |
| 2159 | assert(!InitDone, "invariant")do { if (!(!InitDone)) { (*g_assert_poison) = 'X';; report_vm_error ("/home/daniel/Projects/java/jdk/src/hotspot/share/runtime/objectMonitor.cpp" , 2159, "assert(" "!InitDone" ") failed", "invariant"); ::breakpoint (); } } while (0); |
| 2160 | |
| 2161 | if (!os::is_MP()) { |
| 2162 | Knob_SpinLimit = 0; |
| 2163 | Knob_PreSpin = 0; |
| 2164 | Knob_FixedSpin = -1; |
| 2165 | } |
| 2166 | |
| 2167 | if (UsePerfData) { |
| 2168 | EXCEPTION_MARKExceptionMark __em; JavaThread* __the_thread__ = __em.thread( );; |
| 2169 | #define NEWPERFCOUNTER(n) \ |
| 2170 | { \ |
| 2171 | n = PerfDataManager::create_counter(SUN_RT, #n, PerfData::U_Events, \ |
| 2172 | CHECK__the_thread__); if ((((ThreadShadow*)__the_thread__)->has_pending_exception ())) return ; (void)(0); \ |
| 2173 | } |
| 2174 | #define NEWPERFVARIABLE(n) \ |
| 2175 | { \ |
| 2176 | n = PerfDataManager::create_variable(SUN_RT, #n, PerfData::U_Events, \ |
| 2177 | CHECK__the_thread__); if ((((ThreadShadow*)__the_thread__)->has_pending_exception ())) return ; (void)(0); \ |
| 2178 | } |
| 2179 | NEWPERFCOUNTER(_sync_Inflations); |
| 2180 | NEWPERFCOUNTER(_sync_Deflations); |
| 2181 | NEWPERFCOUNTER(_sync_ContendedLockAttempts); |
| 2182 | NEWPERFCOUNTER(_sync_FutileWakeups); |
| 2183 | NEWPERFCOUNTER(_sync_Parks); |
| 2184 | NEWPERFCOUNTER(_sync_Notifications); |
| 2185 | NEWPERFVARIABLE(_sync_MonExtant); |
| 2186 | #undef NEWPERFCOUNTER |
| 2187 | #undef NEWPERFVARIABLE |
| 2188 | } |
| 2189 | |
| 2190 | _oop_storage = OopStorageSet::create_weak("ObjectSynchronizer Weak", mtSynchronizer); |
| 2191 | |
| 2192 | DEBUG_ONLY(InitDone = true;)InitDone = true; |
| 2193 | } |
| 2194 | |
| 2195 | void ObjectMonitor::print_on(outputStream* st) const { |
| 2196 | // The minimal things to print for markWord printing, more can be added for debugging and logging. |
| 2197 | st->print("{contentions=0x%08x,waiters=0x%08x" |
| 2198 | ",recursions=" INTX_FORMAT"%" "l" "d" ",owner=" INTPTR_FORMAT"0x%016" "l" "x" "}", |
| 2199 | contentions(), waiters(), recursions(), |
| 2200 | p2i(owner())); |
| 2201 | } |
| 2202 | void ObjectMonitor::print() const { print_on(tty); } |
| 2203 | |
| 2204 | #ifdef ASSERT1 |
| 2205 | // Print the ObjectMonitor like a debugger would: |
| 2206 | // |
| 2207 | // (ObjectMonitor) 0x00007fdfb6012e40 = { |
| 2208 | // _header = 0x0000000000000001 |
| 2209 | // _object = 0x000000070ff45fd0 |
| 2210 | // _pad_buf0 = { |
| 2211 | // [0] = '\0' |
| 2212 | // ... |
| 2213 | // [43] = '\0' |
| 2214 | // } |
| 2215 | // _owner = 0x0000000000000000 |
| 2216 | // _previous_owner_tid = 0 |
| 2217 | // _pad_buf1 = { |
| 2218 | // [0] = '\0' |
| 2219 | // ... |
| 2220 | // [47] = '\0' |
| 2221 | // } |
| 2222 | // _next_om = 0x0000000000000000 |
| 2223 | // _recursions = 0 |
| 2224 | // _EntryList = 0x0000000000000000 |
| 2225 | // _cxq = 0x0000000000000000 |
| 2226 | // _succ = 0x0000000000000000 |
| 2227 | // _Responsible = 0x0000000000000000 |
| 2228 | // _Spinner = 0 |
| 2229 | // _SpinDuration = 5000 |
| 2230 | // _contentions = 0 |
| 2231 | // _WaitSet = 0x0000700009756248 |
| 2232 | // _waiters = 1 |
| 2233 | // _WaitSetLock = 0 |
| 2234 | // } |
| 2235 | // |
| 2236 | void ObjectMonitor::print_debug_style_on(outputStream* st) const { |
| 2237 | st->print_cr("(ObjectMonitor*) " INTPTR_FORMAT"0x%016" "l" "x" " = {", p2i(this)); |
| 2238 | st->print_cr(" _header = " INTPTR_FORMAT"0x%016" "l" "x", header().value()); |
| 2239 | st->print_cr(" _object = " INTPTR_FORMAT"0x%016" "l" "x", p2i(object_peek())); |
| 2240 | st->print_cr(" _pad_buf0 = {"); |
| 2241 | st->print_cr(" [0] = '\\0'"); |
| 2242 | st->print_cr(" ..."); |
| 2243 | st->print_cr(" [%d] = '\\0'", (int)sizeof(_pad_buf0) - 1); |
| 2244 | st->print_cr(" }"); |
| 2245 | st->print_cr(" _owner = " INTPTR_FORMAT"0x%016" "l" "x", p2i(owner_raw())); |
| 2246 | st->print_cr(" _previous_owner_tid = " UINT64_FORMAT"%" "l" "u", _previous_owner_tid); |
| 2247 | st->print_cr(" _pad_buf1 = {"); |
| 2248 | st->print_cr(" [0] = '\\0'"); |
| 2249 | st->print_cr(" ..."); |
| 2250 | st->print_cr(" [%d] = '\\0'", (int)sizeof(_pad_buf1) - 1); |
| 2251 | st->print_cr(" }"); |
| 2252 | st->print_cr(" _next_om = " INTPTR_FORMAT"0x%016" "l" "x", p2i(next_om())); |
| 2253 | st->print_cr(" _recursions = " INTX_FORMAT"%" "l" "d", _recursions); |
| 2254 | st->print_cr(" _EntryList = " INTPTR_FORMAT"0x%016" "l" "x", p2i(_EntryList)); |
| 2255 | st->print_cr(" _cxq = " INTPTR_FORMAT"0x%016" "l" "x", p2i(_cxq)); |
| 2256 | st->print_cr(" _succ = " INTPTR_FORMAT"0x%016" "l" "x", p2i(_succ)); |
| 2257 | st->print_cr(" _Responsible = " INTPTR_FORMAT"0x%016" "l" "x", p2i(_Responsible)); |
| 2258 | st->print_cr(" _Spinner = %d", _Spinner); |
| 2259 | st->print_cr(" _SpinDuration = %d", _SpinDuration); |
| 2260 | st->print_cr(" _contentions = %d", contentions()); |
| 2261 | st->print_cr(" _WaitSet = " INTPTR_FORMAT"0x%016" "l" "x", p2i(_WaitSet)); |
| 2262 | st->print_cr(" _waiters = %d", _waiters); |
| 2263 | st->print_cr(" _WaitSetLock = %d", _WaitSetLock); |
| 2264 | st->print_cr("}"); |
| 2265 | } |
| 2266 | #endif |