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 #ifndef SHARE_RUNTIME_MUTEXLOCKER_HPP
26 #define SHARE_RUNTIME_MUTEXLOCKER_HPP
27
28 #include "memory/allocation.hpp"
29 #include "runtime/flags/flagSetting.hpp"
30 #include "runtime/mutex.hpp"
31
32 class Thread;
33
34 // Mutexes used in the VM.
35
36 extern Mutex* NMethodState_lock; // a lock used to guard a compiled method state
37 extern Monitor* SystemDictionary_lock; // a lock on the system dictionary
38 extern Mutex* InvokeMethodTypeTable_lock;
39 extern Monitor* InvokeMethodIntrinsicTable_lock;
40 extern Mutex* SharedDictionary_lock; // a lock on the CDS shared dictionary
41 extern Monitor* ClassInitError_lock; // a lock on the class initialization error table
42 extern Mutex* Module_lock; // a lock on module and package related data structures
43 extern Mutex* CompiledIC_lock; // a lock used to guard compiled IC patching and access
44 extern Mutex* VMStatistic_lock; // a lock used to guard statistics count increment
45 extern Mutex* JmethodIdCreation_lock; // a lock on creating JNI method identifiers
46 extern Mutex* JfieldIdCreation_lock; // a lock on creating JNI static field identifiers
47 extern Monitor* JNICritical_lock; // a lock used while synchronizing with threads entering/leaving JNI critical regions
48 extern Mutex* JvmtiThreadState_lock; // a lock on modification of JVMTI thread data
49 extern Monitor* EscapeBarrier_lock; // a lock to sync reallocating and relocking objects because of JVMTI access
50 extern Monitor* JvmtiVTMSTransition_lock; // a lock for Virtual Thread Mount State transition (VTMS transition) management
63 extern Mutex* RetData_lock; // a lock on installation of RetData inside method data
64 extern Monitor* VMOperation_lock; // a lock on queue of vm_operations waiting to execute
65 extern Monitor* ThreadsLockThrottle_lock; // used by Thread start/exit to reduce competition for Threads_lock,
66 // so a VM thread calling a safepoint is prioritized
67 extern Monitor* Threads_lock; // a lock on the Threads table of active Java threads
68 // (also used by Safepoints too to block threads creation/destruction)
69 extern Mutex* NonJavaThreadsList_lock; // a lock on the NonJavaThreads list
70 extern Mutex* NonJavaThreadsListSync_lock; // a lock for NonJavaThreads list synchronization
71 extern Monitor* CGC_lock; // used for coordination between
72 // fore- & background GC threads.
73 extern Monitor* STS_lock; // used for joining/leaving SuspendibleThreadSet.
74 extern Monitor* G1OldGCCount_lock; // in support of "concurrent" full gc
75 extern Mutex* G1RareEvent_lock; // Synchronizes (rare) parallel GC operations.
76 extern Mutex* G1DetachedRefinementStats_lock; // Lock protecting detached refinement stats
77 extern Mutex* MarkStackFreeList_lock; // Protects access to the global mark stack free list.
78 extern Mutex* MarkStackChunkList_lock; // Protects access to the global mark stack chunk list.
79 extern Mutex* MonitoringSupport_lock; // Protects updates to the serviceability memory pools and allocated memory high water mark.
80 extern Monitor* ConcurrentGCBreakpoints_lock; // Protects concurrent GC breakpoint management
81 extern Mutex* Compile_lock; // a lock held when Compilation is updating code (used to block CodeCache traversal, CHA updates, etc)
82 extern Monitor* MethodCompileQueue_lock; // a lock held when method compilations are enqueued, dequeued
83 extern Monitor* CompileThread_lock; // a lock held by compile threads during compilation system initialization
84 extern Monitor* Compilation_lock; // a lock used to pause compilation
85 extern Mutex* CompileTaskAlloc_lock; // a lock held when CompileTasks are allocated
86 extern Mutex* CompileStatistics_lock; // a lock held when updating compilation statistics
87 extern Mutex* DirectivesStack_lock; // a lock held when mutating the dirstack and ref counting directives
88 extern Monitor* Terminator_lock; // a lock used to guard termination of the vm
89 extern Monitor* InitCompleted_lock; // a lock used to signal threads waiting on init completed
90 extern Monitor* BeforeExit_lock; // a lock used to guard cleanups and shutdown hooks
91 extern Monitor* Notify_lock; // a lock used to synchronize the start-up of the vm
92 extern Mutex* ExceptionCache_lock; // a lock used to synchronize exception cache updates
93
94 #ifndef PRODUCT
95 extern Mutex* FullGCALot_lock; // a lock to make FullGCALot MT safe
96 #endif // PRODUCT
97
98 extern Mutex* RawMonitor_lock;
99 extern Mutex* PerfDataMemAlloc_lock; // a lock on the allocator for PerfData memory for performance data
100 extern Mutex* PerfDataManager_lock; // a long on access to PerfDataManager resources
101
102 extern Mutex* FreeList_lock; // protects the free region list during safepoints
103 extern Mutex* OldSets_lock; // protects the old region sets
104 extern Mutex* Uncommit_lock; // protects the uncommit list when not at safepoints
105 extern Monitor* RootRegionScan_lock; // used to notify that the CM threads have finished scanning the IM snapshot regions
112 extern Monitor* RedefineClasses_lock; // locks classes from parallel redefinition
113 extern Mutex* Verify_lock; // synchronize initialization of verify library
114 extern Monitor* ThreadsSMRDelete_lock; // Used by ThreadsSMRSupport to take pressure off the Threads_lock
115 extern Mutex* ThreadIdTableCreate_lock; // Used by ThreadIdTable to lazily create the thread id table
116 extern Mutex* SharedDecoder_lock; // serializes access to the decoder during normal (not error reporting) use
117 extern Mutex* DCmdFactory_lock; // serialize access to DCmdFactory information
118 extern Mutex* NMTQuery_lock; // serialize NMT Dcmd queries
119 extern Mutex* NMTCompilationCostHistory_lock; // guards NMT compilation cost history
120 extern Mutex* NmtVirtualMemory_lock; // guards NMT virtual memory updates
121 #if INCLUDE_CDS
122 #if INCLUDE_JVMTI
123 extern Mutex* CDSClassFileStream_lock; // FileMapInfo::open_stream_for_jvmti
124 #endif
125 extern Mutex* DumpTimeTable_lock; // SystemDictionaryShared::_dumptime_table
126 extern Mutex* CDSLambda_lock; // LambdaProxyClassDictionary::find_lambda_proxy_class
127 extern Mutex* DumpRegion_lock; // Symbol::operator new(size_t sz, int len)
128 extern Mutex* ClassListFile_lock; // ClassListWriter()
129 extern Mutex* UnregisteredClassesTable_lock; // UnregisteredClassesTableTable
130 extern Mutex* LambdaFormInvokers_lock; // Protecting LambdaFormInvokers::_lambdaform_lines
131 extern Mutex* ScratchObjects_lock; // Protecting _scratch_xxx_table in heapShared.cpp
132 #endif // INCLUDE_CDS
133 #if INCLUDE_JFR
134 extern Mutex* JfrStacktrace_lock; // used to guard access to the JFR stacktrace table
135 extern Monitor* JfrMsg_lock; // protects JFR messaging
136 extern Mutex* JfrBuffer_lock; // protects JFR buffer operations
137 extern Monitor* JfrThreadSampler_lock; // used to suspend/resume JFR thread sampler
138 #endif
139
140 extern Mutex* Metaspace_lock; // protects Metaspace virtualspace and chunk expansions
141 extern Monitor* MetaspaceCritical_lock; // synchronizes failed metaspace allocations that risk throwing metaspace OOM
142 extern Mutex* ClassLoaderDataGraph_lock; // protects CLDG list, needed for concurrent unloading
143
144
145 extern Mutex* CodeHeapStateAnalytics_lock; // lock print functions against concurrent analyze functions.
146 // Only used locally in PrintCodeCacheLayout processing.
147
148 extern Mutex* ExternalsRecorder_lock; // used to guard access to the external addresses table
149
150 extern Monitor* ContinuationRelativize_lock;
151
169 // See orderAccess.hpp. We assume throughout the VM that MutexLocker's
170 // and friends constructors do a fence, a lock and an acquire *in that
171 // order*. And that their destructors do a release and unlock, in *that*
172 // order. If their implementations change such that these assumptions
173 // are violated, a whole lot of code will break.
174
175 // for debugging: check that we're already owning this lock (or are at a safepoint / handshake)
176 #ifdef ASSERT
177 void assert_locked_or_safepoint(const Mutex* lock);
178 void assert_lock_strong(const Mutex* lock);
179 #else
180 #define assert_locked_or_safepoint(lock)
181 #define assert_lock_strong(lock)
182 #endif
183
184 // Internal implementation. Skips on null Mutex.
185 // Subclasses enforce stronger invariants.
186 class MutexLockerImpl: public StackObj {
187 protected:
188 Mutex* _mutex;
189
190 MutexLockerImpl(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
191 _mutex(mutex) {
192 bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
193 if (_mutex != nullptr) {
194 if (no_safepoint_check) {
195 _mutex->lock_without_safepoint_check();
196 } else {
197 _mutex->lock();
198 }
199 }
200 }
201
202 MutexLockerImpl(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
203 _mutex(mutex) {
204 bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
205 if (_mutex != nullptr) {
206 if (no_safepoint_check) {
207 _mutex->lock_without_safepoint_check(thread);
208 } else {
209 _mutex->lock(thread);
210 }
211 }
212 }
213
214 ~MutexLockerImpl() {
215 if (_mutex != nullptr) {
216 assert_lock_strong(_mutex);
217 _mutex->unlock();
218 }
219 }
220
221 public:
222 static void post_initialize();
223 };
224
225 // Simplest mutex locker.
226 // Does not allow null mutexes.
227 class MutexLocker: public MutexLockerImpl {
228 public:
229 MutexLocker(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
230 MutexLockerImpl(mutex, flag) {
231 assert(mutex != nullptr, "null mutex not allowed");
232 }
233
234 MutexLocker(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
235 MutexLockerImpl(thread, mutex, flag) {
236 assert(mutex != nullptr, "null mutex not allowed");
237 }
238 };
239
240 // Conditional mutex locker.
241 // Like MutexLocker above, but only locks when condition is true.
242 class ConditionalMutexLocker: public MutexLockerImpl {
|
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 #ifndef SHARE_RUNTIME_MUTEXLOCKER_HPP
26 #define SHARE_RUNTIME_MUTEXLOCKER_HPP
27
28 #include "logging/log.hpp"
29 #include "memory/allocation.hpp"
30 #include "runtime/flags/flagSetting.hpp"
31 #include "runtime/mutex.hpp"
32 #include "runtime/perfData.hpp"
33 #include "runtime/thread.hpp"
34
35 class Thread;
36
37 // Mutexes used in the VM.
38
39 extern Mutex* NMethodState_lock; // a lock used to guard a compiled method state
40 extern Monitor* SystemDictionary_lock; // a lock on the system dictionary
41 extern Mutex* InvokeMethodTypeTable_lock;
42 extern Monitor* InvokeMethodIntrinsicTable_lock;
43 extern Mutex* SharedDictionary_lock; // a lock on the CDS shared dictionary
44 extern Monitor* ClassInitError_lock; // a lock on the class initialization error table
45 extern Mutex* Module_lock; // a lock on module and package related data structures
46 extern Mutex* CompiledIC_lock; // a lock used to guard compiled IC patching and access
47 extern Mutex* VMStatistic_lock; // a lock used to guard statistics count increment
48 extern Mutex* JmethodIdCreation_lock; // a lock on creating JNI method identifiers
49 extern Mutex* JfieldIdCreation_lock; // a lock on creating JNI static field identifiers
50 extern Monitor* JNICritical_lock; // a lock used while synchronizing with threads entering/leaving JNI critical regions
51 extern Mutex* JvmtiThreadState_lock; // a lock on modification of JVMTI thread data
52 extern Monitor* EscapeBarrier_lock; // a lock to sync reallocating and relocking objects because of JVMTI access
53 extern Monitor* JvmtiVTMSTransition_lock; // a lock for Virtual Thread Mount State transition (VTMS transition) management
66 extern Mutex* RetData_lock; // a lock on installation of RetData inside method data
67 extern Monitor* VMOperation_lock; // a lock on queue of vm_operations waiting to execute
68 extern Monitor* ThreadsLockThrottle_lock; // used by Thread start/exit to reduce competition for Threads_lock,
69 // so a VM thread calling a safepoint is prioritized
70 extern Monitor* Threads_lock; // a lock on the Threads table of active Java threads
71 // (also used by Safepoints too to block threads creation/destruction)
72 extern Mutex* NonJavaThreadsList_lock; // a lock on the NonJavaThreads list
73 extern Mutex* NonJavaThreadsListSync_lock; // a lock for NonJavaThreads list synchronization
74 extern Monitor* CGC_lock; // used for coordination between
75 // fore- & background GC threads.
76 extern Monitor* STS_lock; // used for joining/leaving SuspendibleThreadSet.
77 extern Monitor* G1OldGCCount_lock; // in support of "concurrent" full gc
78 extern Mutex* G1RareEvent_lock; // Synchronizes (rare) parallel GC operations.
79 extern Mutex* G1DetachedRefinementStats_lock; // Lock protecting detached refinement stats
80 extern Mutex* MarkStackFreeList_lock; // Protects access to the global mark stack free list.
81 extern Mutex* MarkStackChunkList_lock; // Protects access to the global mark stack chunk list.
82 extern Mutex* MonitoringSupport_lock; // Protects updates to the serviceability memory pools and allocated memory high water mark.
83 extern Monitor* ConcurrentGCBreakpoints_lock; // Protects concurrent GC breakpoint management
84 extern Mutex* Compile_lock; // a lock held when Compilation is updating code (used to block CodeCache traversal, CHA updates, etc)
85 extern Monitor* MethodCompileQueue_lock; // a lock held when method compilations are enqueued, dequeued
86 extern Monitor* MethodCompileQueueC1_lock; // a lock held when method compilations are enqueued, dequeued
87 extern Monitor* MethodCompileQueueC2_lock; // a lock held when method compilations are enqueued, dequeued
88 extern Monitor* MethodCompileQueueC3_lock; // a lock held when method compilations are enqueued, dequeued
89 extern Monitor* MethodCompileQueueSC1_lock; // a lock held when method compilations are enqueued, dequeued
90 extern Monitor* MethodCompileQueueSC2_lock; // a lock held when method compilations are enqueued, dequeued
91 extern Monitor* CompileThread_lock; // a lock held by compile threads during compilation system initialization
92 extern Monitor* Compilation_lock; // a lock used to pause compilation
93 extern Mutex* TrainingData_lock; // a lock used when accessing training records
94 extern Monitor* TrainingReplayQueue_lock; // a lock held when class are added/removed to the training replay queue
95 extern Monitor* CompileTaskAlloc_lock; // a lock held when CompileTasks are allocated
96 extern Mutex* CompileStatistics_lock; // a lock held when updating compilation statistics
97 extern Mutex* DirectivesStack_lock; // a lock held when mutating the dirstack and ref counting directives
98 extern Monitor* Terminator_lock; // a lock used to guard termination of the vm
99 extern Monitor* InitCompleted_lock; // a lock used to signal threads waiting on init completed
100 extern Monitor* BeforeExit_lock; // a lock used to guard cleanups and shutdown hooks
101 extern Monitor* Notify_lock; // a lock used to synchronize the start-up of the vm
102 extern Mutex* ExceptionCache_lock; // a lock used to synchronize exception cache updates
103
104 #ifndef PRODUCT
105 extern Mutex* FullGCALot_lock; // a lock to make FullGCALot MT safe
106 #endif // PRODUCT
107
108 extern Mutex* RawMonitor_lock;
109 extern Mutex* PerfDataMemAlloc_lock; // a lock on the allocator for PerfData memory for performance data
110 extern Mutex* PerfDataManager_lock; // a long on access to PerfDataManager resources
111
112 extern Mutex* FreeList_lock; // protects the free region list during safepoints
113 extern Mutex* OldSets_lock; // protects the old region sets
114 extern Mutex* Uncommit_lock; // protects the uncommit list when not at safepoints
115 extern Monitor* RootRegionScan_lock; // used to notify that the CM threads have finished scanning the IM snapshot regions
122 extern Monitor* RedefineClasses_lock; // locks classes from parallel redefinition
123 extern Mutex* Verify_lock; // synchronize initialization of verify library
124 extern Monitor* ThreadsSMRDelete_lock; // Used by ThreadsSMRSupport to take pressure off the Threads_lock
125 extern Mutex* ThreadIdTableCreate_lock; // Used by ThreadIdTable to lazily create the thread id table
126 extern Mutex* SharedDecoder_lock; // serializes access to the decoder during normal (not error reporting) use
127 extern Mutex* DCmdFactory_lock; // serialize access to DCmdFactory information
128 extern Mutex* NMTQuery_lock; // serialize NMT Dcmd queries
129 extern Mutex* NMTCompilationCostHistory_lock; // guards NMT compilation cost history
130 extern Mutex* NmtVirtualMemory_lock; // guards NMT virtual memory updates
131 #if INCLUDE_CDS
132 #if INCLUDE_JVMTI
133 extern Mutex* CDSClassFileStream_lock; // FileMapInfo::open_stream_for_jvmti
134 #endif
135 extern Mutex* DumpTimeTable_lock; // SystemDictionaryShared::_dumptime_table
136 extern Mutex* CDSLambda_lock; // LambdaProxyClassDictionary::find_lambda_proxy_class
137 extern Mutex* DumpRegion_lock; // Symbol::operator new(size_t sz, int len)
138 extern Mutex* ClassListFile_lock; // ClassListWriter()
139 extern Mutex* UnregisteredClassesTable_lock; // UnregisteredClassesTableTable
140 extern Mutex* LambdaFormInvokers_lock; // Protecting LambdaFormInvokers::_lambdaform_lines
141 extern Mutex* ScratchObjects_lock; // Protecting _scratch_xxx_table in heapShared.cpp
142 extern Mutex* ArchivedObjectTables_lock; // Protecting the table used by HeapShared::get_archived_object_permanent_index()
143 extern Mutex* FinalImageRecipes_lock; // Protecting the tables used by FinalImageRecipes.
144 #endif // INCLUDE_CDS
145 #if INCLUDE_JFR
146 extern Mutex* JfrStacktrace_lock; // used to guard access to the JFR stacktrace table
147 extern Monitor* JfrMsg_lock; // protects JFR messaging
148 extern Mutex* JfrBuffer_lock; // protects JFR buffer operations
149 extern Monitor* JfrThreadSampler_lock; // used to suspend/resume JFR thread sampler
150 #endif
151
152 extern Mutex* Metaspace_lock; // protects Metaspace virtualspace and chunk expansions
153 extern Monitor* MetaspaceCritical_lock; // synchronizes failed metaspace allocations that risk throwing metaspace OOM
154 extern Mutex* ClassLoaderDataGraph_lock; // protects CLDG list, needed for concurrent unloading
155
156
157 extern Mutex* CodeHeapStateAnalytics_lock; // lock print functions against concurrent analyze functions.
158 // Only used locally in PrintCodeCacheLayout processing.
159
160 extern Mutex* ExternalsRecorder_lock; // used to guard access to the external addresses table
161
162 extern Monitor* ContinuationRelativize_lock;
163
181 // See orderAccess.hpp. We assume throughout the VM that MutexLocker's
182 // and friends constructors do a fence, a lock and an acquire *in that
183 // order*. And that their destructors do a release and unlock, in *that*
184 // order. If their implementations change such that these assumptions
185 // are violated, a whole lot of code will break.
186
187 // for debugging: check that we're already owning this lock (or are at a safepoint / handshake)
188 #ifdef ASSERT
189 void assert_locked_or_safepoint(const Mutex* lock);
190 void assert_lock_strong(const Mutex* lock);
191 #else
192 #define assert_locked_or_safepoint(lock)
193 #define assert_lock_strong(lock)
194 #endif
195
196 // Internal implementation. Skips on null Mutex.
197 // Subclasses enforce stronger invariants.
198 class MutexLockerImpl: public StackObj {
199 protected:
200 Mutex* _mutex;
201 bool _prof;
202 elapsedTimer _before;
203 elapsedTimer _after;
204
205 private:
206 static PerfCounter** _perf_lock_count;
207 static PerfCounter** _perf_lock_wait_time;
208 static PerfCounter** _perf_lock_hold_time;
209
210 public:
211
212 MutexLockerImpl(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
213 _mutex(mutex), _prof(ProfileVMLocks && Thread::current_or_null() != nullptr && Thread::current()->profile_vm_locks()) {
214
215 bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
216 if (_mutex != nullptr) {
217 if (_prof) { _before.start(); } // before
218
219 if (no_safepoint_check) {
220 _mutex->lock_without_safepoint_check();
221 } else {
222 _mutex->lock();
223 }
224
225 if (_prof) { _before.stop(); _after.start(); } // after
226 }
227 }
228
229 MutexLockerImpl(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
230 _mutex(mutex), _prof(thread->profile_vm_locks()) {
231
232 if (_prof) { _before.start(); } // before
233
234 bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
235 if (_mutex != nullptr) {
236 if (no_safepoint_check) {
237 _mutex->lock_without_safepoint_check(thread);
238 } else {
239 _mutex->lock(thread);
240 }
241 }
242
243 if (_prof) { _before.stop(); _after.start(); } // after
244 }
245
246 ~MutexLockerImpl() {
247 if (_mutex != nullptr) {
248 assert_lock_strong(_mutex);
249 _mutex->unlock();
250
251 if (_mutex->id() == -1) {
252 log_trace(init)("Unnamed unclassified lock: %s", _mutex->name());
253 }
254
255 if (_prof) {
256 assert(UsePerfData, "required");
257 _after.stop();
258 _perf_lock_count [_mutex->id() + 1]->inc();
259 _perf_lock_wait_time[_mutex->id() + 1]->inc(_before.ticks());
260 _perf_lock_hold_time[_mutex->id() + 1]->inc(_after.ticks());
261 }
262 }
263 }
264
265 private:
266 static void print_counter_on(outputStream* st, const char* name, bool is_unique, int idx);
267
268 public:
269 static int name2id(const char* name);
270
271 static void post_initialize();
272 static void init_counters();
273 static void print_counters_on(outputStream* st);
274 };
275
276 // Simplest mutex locker.
277 // Does not allow null mutexes.
278 class MutexLocker: public MutexLockerImpl {
279 public:
280 MutexLocker(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
281 MutexLockerImpl(mutex, flag) {
282 assert(mutex != nullptr, "null mutex not allowed");
283 }
284
285 MutexLocker(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
286 MutexLockerImpl(thread, mutex, flag) {
287 assert(mutex != nullptr, "null mutex not allowed");
288 }
289 };
290
291 // Conditional mutex locker.
292 // Like MutexLocker above, but only locks when condition is true.
293 class ConditionalMutexLocker: public MutexLockerImpl {
|