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src/hotspot/share/runtime/thread.cpp

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rev 47862 : imported patch 10.07.open.rebase_20171110.dcubed
rev 47863 : imported patch 10.08.open.rebase_20171114.rehn
rev 47864 : imported patch 10.09.open.TLH_hang_fix.rehn
rev 47865 : dholmes CR: Fix indents, trailing spaces and various typos. Add descriptions for the '_cnt', '_max' and '_times" fields, add impl notes to document the type choices.
rev 47866 : robinw CR: Fix some inefficient code, update some comments, fix some indents, and add some 'const' specifiers.

*** 69,93 **** #include "runtime/init.hpp" #include "runtime/interfaceSupport.hpp" #include "runtime/java.hpp" #include "runtime/javaCalls.hpp" #include "runtime/jniPeriodicChecker.hpp" - #include "runtime/timerTrace.hpp" #include "runtime/memprofiler.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/objectMonitor.hpp" #include "runtime/orderAccess.inline.hpp" #include "runtime/osThread.hpp" #include "runtime/safepoint.hpp" #include "runtime/safepointMechanism.inline.hpp" #include "runtime/sharedRuntime.hpp" #include "runtime/statSampler.hpp" #include "runtime/stubRoutines.hpp" #include "runtime/sweeper.hpp" #include "runtime/task.hpp" #include "runtime/thread.inline.hpp" #include "runtime/threadCritical.hpp" #include "runtime/vframe.hpp" #include "runtime/vframeArray.hpp" #include "runtime/vframe_hp.hpp" #include "runtime/vmThread.hpp" #include "runtime/vm_operations.hpp" --- 69,96 ---- #include "runtime/init.hpp" #include "runtime/interfaceSupport.hpp" #include "runtime/java.hpp" #include "runtime/javaCalls.hpp" #include "runtime/jniPeriodicChecker.hpp" #include "runtime/memprofiler.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/objectMonitor.hpp" #include "runtime/orderAccess.inline.hpp" #include "runtime/osThread.hpp" + #include "runtime/prefetch.inline.hpp" #include "runtime/safepoint.hpp" #include "runtime/safepointMechanism.inline.hpp" #include "runtime/sharedRuntime.hpp" #include "runtime/statSampler.hpp" #include "runtime/stubRoutines.hpp" #include "runtime/sweeper.hpp" #include "runtime/task.hpp" #include "runtime/thread.inline.hpp" #include "runtime/threadCritical.hpp" + #include "runtime/threadSMR.inline.hpp" + #include "runtime/timer.hpp" + #include "runtime/timerTrace.hpp" #include "runtime/vframe.hpp" #include "runtime/vframeArray.hpp" #include "runtime/vframe_hp.hpp" #include "runtime/vmThread.hpp" #include "runtime/vm_operations.hpp"
*** 102,111 **** --- 105,115 ---- #include "utilities/defaultStream.hpp" #include "utilities/dtrace.hpp" #include "utilities/events.hpp" #include "utilities/macros.hpp" #include "utilities/preserveException.hpp" + #include "utilities/resourceHash.hpp" #include "utilities/vmError.hpp" #if INCLUDE_ALL_GCS #include "gc/cms/concurrentMarkSweepThread.hpp" #include "gc/g1/concurrentMarkThread.inline.hpp" #include "gc/parallel/pcTasks.hpp"
*** 193,209 **** } } void Thread::operator delete(void* p) { if (UseBiasedLocking) { ! void* real_malloc_addr = ((Thread*) p)->_real_malloc_address; ! FreeHeap(real_malloc_addr); } else { FreeHeap(p); } } // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread, // JavaThread --- 197,219 ---- } } void Thread::operator delete(void* p) { if (UseBiasedLocking) { ! FreeHeap(((Thread*) p)->_real_malloc_address); } else { FreeHeap(p); } } + void JavaThread::smr_delete() { + if (_on_thread_list) { + Threads::smr_delete(this); + } else { + delete this; + } + } // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread, // JavaThread
*** 225,234 **** --- 235,247 ---- set_free_handle_block(NULL); set_last_handle_mark(NULL); // This initial value ==> never claimed. _oops_do_parity = 0; + _threads_hazard_ptr = NULL; + _nested_threads_hazard_ptr = NULL; + _nested_threads_hazard_ptr_cnt = 0; // the handle mark links itself to last_handle_mark new HandleMark(this); // plain initialization
*** 396,408 **** void Thread::run() { ShouldNotReachHere(); } #ifdef ASSERT ! // Private method to check for dangling thread pointer ! void check_for_dangling_thread_pointer(Thread *thread) { ! assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(), "possibility of dangling Thread pointer"); } #endif ThreadPriority Thread::get_priority(const Thread* const thread) { --- 409,427 ---- void Thread::run() { ShouldNotReachHere(); } #ifdef ASSERT ! // A JavaThread is considered "dangling" if it is not the current ! // thread, has been added the Threads list, the system is not at a ! // safepoint and the Thread is not "protected". ! // ! void Thread::check_for_dangling_thread_pointer(Thread *thread) { ! assert(!thread->is_Java_thread() || Thread::current() == thread || ! !((JavaThread *) thread)->on_thread_list() || ! SafepointSynchronize::is_at_safepoint() || ! Threads::is_a_protected_JavaThread_with_lock((JavaThread *) thread), "possibility of dangling Thread pointer"); } #endif ThreadPriority Thread::get_priority(const Thread* const thread) {
*** 730,739 **** --- 749,789 ---- // thread did not suspend after all our retries *bits |= 0x00200000; return false; } + // Called from API entry points which perform stack walking. If the + // associated JavaThread is the current thread, then wait_for_suspend + // is not used. Otherwise, it determines if we should wait for the + // "other" thread to complete external suspension. (NOTE: in future + // releases the suspension mechanism should be reimplemented so this + // is not necessary.) + // + bool + JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) { + if (this != JavaThread::current()) { + // "other" threads require special handling. + if (wait_for_suspend) { + // We are allowed to wait for the external suspend to complete + // so give the other thread a chance to get suspended. + if (!wait_for_ext_suspend_completion(SuspendRetryCount, + SuspendRetryDelay, bits)) { + // Didn't make it so let the caller know. + return false; + } + } + // We aren't allowed to wait for the external suspend to complete + // so if the other thread isn't externally suspended we need to + // let the caller know. + else if (!is_ext_suspend_completed_with_lock(bits)) { + return false; + } + } + + return true; + } + #ifndef PRODUCT void JavaThread::record_jump(address target, address instr, const char* file, int line) { // This should not need to be atomic as the only way for simultaneous
*** 808,820 **** --- 858,894 ---- } st->print("tid=" INTPTR_FORMAT " ", p2i(this)); ext().print_on(st); osthread()->print_on(st); } + if (_threads_hazard_ptr != NULL) { + st->print("_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr)); + } + if (_nested_threads_hazard_ptr != NULL) { + print_nested_threads_hazard_ptrs_on(st); + } + st->print(" "); debug_only(if (WizardMode) print_owned_locks_on(st);) } + void Thread::print_nested_threads_hazard_ptrs_on(outputStream* st) const { + assert(_nested_threads_hazard_ptr != NULL, "must be set to print"); + + if (EnableThreadSMRStatistics) { + st->print(", _nested_threads_hazard_ptr_cnt=%u", _nested_threads_hazard_ptr_cnt); + } + st->print(", _nested_threads_hazard_ptrs="); + for (NestedThreadsList* node = _nested_threads_hazard_ptr; node != NULL; + node = node->next()) { + if (node != _nested_threads_hazard_ptr) { + // First node does not need a comma-space separator. + st->print(", "); + } + st->print(INTPTR_FORMAT, p2i(node->t_list())); + } + } + // Thread::print_on_error() is called by fatal error handler. Don't use // any lock or allocate memory. void Thread::print_on_error(outputStream* st, char* buf, int buflen) const { assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
*** 832,841 **** --- 906,922 ---- p2i(stack_end()), p2i(stack_base())); if (osthread()) { st->print(" [id=%d]", osthread()->thread_id()); } + + if (_threads_hazard_ptr != NULL) { + st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr)); + } + if (_nested_threads_hazard_ptr != NULL) { + print_nested_threads_hazard_ptrs_on(st); + } } void Thread::print_value_on(outputStream* st) const { if (is_Named_thread()) { st->print(" \"%s\" ", name());
*** 869,880 **** #endif #ifndef PRODUCT ! // The flag: potential_vm_operation notifies if this particular safepoint state could potential ! // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that // no threads which allow_vm_block's are held void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) { // Check if current thread is allowed to block at a safepoint if (!(_allow_safepoint_count == 0)) { fatal("Possible safepoint reached by thread that does not allow it"); --- 950,961 ---- #endif #ifndef PRODUCT ! // The flag: potential_vm_operation notifies if this particular safepoint state could potentially ! // invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that // no threads which allow_vm_block's are held void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) { // Check if current thread is allowed to block at a safepoint if (!(_allow_safepoint_count == 0)) { fatal("Possible safepoint reached by thread that does not allow it");
*** 1396,1410 **** return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread(); } void JavaThread::collect_counters(typeArrayOop array) { if (JVMCICounterSize > 0) { MutexLocker tl(Threads_lock); for (int i = 0; i < array->length(); i++) { array->long_at_put(i, _jvmci_old_thread_counters[i]); } ! for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) { if (jvmci_counters_include(tp)) { for (int i = 0; i < array->length(); i++) { array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]); } } --- 1477,1494 ---- return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread(); } void JavaThread::collect_counters(typeArrayOop array) { if (JVMCICounterSize > 0) { + // dcubed - Looks like the Threads_lock is for stable access + // to _jvmci_old_thread_counters and _jvmci_counters. MutexLocker tl(Threads_lock); + JavaThreadIteratorWithHandle jtiwh; for (int i = 0; i < array->length(); i++) { array->long_at_put(i, _jvmci_old_thread_counters[i]); } ! for (; JavaThread *tp = jtiwh.next(); ) { if (jvmci_counters_include(tp)) { for (int i = 0; i < array->length(); i++) { array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]); } }
*** 1433,1442 **** --- 1517,1527 ---- set_deopt_mark(NULL); set_deopt_compiled_method(NULL); clear_must_deopt_id(); set_monitor_chunks(NULL); set_next(NULL); + _on_thread_list = false; set_thread_state(_thread_new); _terminated = _not_terminated; _privileged_stack_top = NULL; _array_for_gc = NULL; _suspend_equivalent = false;
*** 1713,1728 **** } DTRACE_THREAD_PROBE(stop, this); this->exit(false); ! delete this; } static void ensure_join(JavaThread* thread) { ! // We do not need to grap the Threads_lock, since we are operating on ourself. Handle threadObj(thread, thread->threadObj()); assert(threadObj.not_null(), "java thread object must exist"); ObjectLocker lock(threadObj, thread); // Ignore pending exception (ThreadDeath), since we are exiting anyway thread->clear_pending_exception(); --- 1798,1813 ---- } DTRACE_THREAD_PROBE(stop, this); this->exit(false); ! this->smr_delete(); } static void ensure_join(JavaThread* thread) { ! // We do not need to grab the Threads_lock, since we are operating on ourself. Handle threadObj(thread, thread->threadObj()); assert(threadObj.not_null(), "java thread object must exist"); ObjectLocker lock(threadObj, thread); // Ignore pending exception (ThreadDeath), since we are exiting anyway thread->clear_pending_exception();
*** 1740,1749 **** --- 1825,1843 ---- // For any new cleanup additions, please check to see if they need to be applied to // cleanup_failed_attach_current_thread as well. void JavaThread::exit(bool destroy_vm, ExitType exit_type) { assert(this == JavaThread::current(), "thread consistency check"); + elapsedTimer _timer_exit_phase1; + elapsedTimer _timer_exit_phase2; + elapsedTimer _timer_exit_phase3; + elapsedTimer _timer_exit_phase4; + + if (log_is_enabled(Debug, os, thread, timer)) { + _timer_exit_phase1.start(); + } + HandleMark hm(this); Handle uncaught_exception(this, this->pending_exception()); this->clear_pending_exception(); Handle threadObj(this, this->threadObj()); assert(threadObj.not_null(), "Java thread object should be created");
*** 1839,1854 **** --- 1933,1956 ---- // no more external suspends are allowed at this point } else { // before_exit() has already posted JVMTI THREAD_END events } + if (log_is_enabled(Debug, os, thread, timer)) { + _timer_exit_phase1.stop(); + _timer_exit_phase2.start(); + } // Notify waiters on thread object. This has to be done after exit() is called // on the thread (if the thread is the last thread in a daemon ThreadGroup the // group should have the destroyed bit set before waiters are notified). ensure_join(this); assert(!this->has_pending_exception(), "ensure_join should have cleared"); + if (log_is_enabled(Debug, os, thread, timer)) { + _timer_exit_phase2.stop(); + _timer_exit_phase3.start(); + } // 6282335 JNI DetachCurrentThread spec states that all Java monitors // held by this thread must be released. The spec does not distinguish // between JNI-acquired and regular Java monitors. We can only see // regular Java monitors here if monitor enter-exit matching is broken. //
*** 1912,1927 **** log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").", exit_type == JavaThread::normal_exit ? "exiting" : "detaching", os::current_thread_id()); // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread Threads::remove(this); ! // If someone set a handshake on us just as we entered exit path, we simple cancel it. ! if (ThreadLocalHandshakes) { ! cancel_handshake(); } } #if INCLUDE_ALL_GCS // Flush G1-related queues. --- 2014,2043 ---- log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").", exit_type == JavaThread::normal_exit ? "exiting" : "detaching", os::current_thread_id()); + if (log_is_enabled(Debug, os, thread, timer)) { + _timer_exit_phase3.stop(); + _timer_exit_phase4.start(); + } // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread Threads::remove(this); ! if (log_is_enabled(Debug, os, thread, timer)) { ! _timer_exit_phase4.stop(); ! ResourceMark rm(this); ! log_debug(os, thread, timer)("name='%s'" ! ", exit-phase1=" JLONG_FORMAT ! ", exit-phase2=" JLONG_FORMAT ! ", exit-phase3=" JLONG_FORMAT ! ", exit-phase4=" JLONG_FORMAT, ! get_thread_name(), ! _timer_exit_phase1.milliseconds(), ! _timer_exit_phase2.milliseconds(), ! _timer_exit_phase3.milliseconds(), ! _timer_exit_phase4.milliseconds()); } } #if INCLUDE_ALL_GCS // Flush G1-related queues.
*** 1978,1988 **** flush_barrier_queues(); } #endif // INCLUDE_ALL_GCS Threads::remove(this); ! delete this; } --- 2094,2104 ---- flush_barrier_queues(); } #endif // INCLUDE_ALL_GCS Threads::remove(this); ! this->smr_delete(); }
*** 2233,2247 **** // + Target thread will not execute any new bytecode (that's why we need to // force a safepoint) // + Target thread will not enter any new monitors // void JavaThread::java_suspend() { ! { MutexLocker mu(Threads_lock); ! if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) { return; } - } { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag); if (!is_external_suspend()) { // a racing resume has cancelled us; bail out now return; --- 2349,2362 ---- // + Target thread will not execute any new bytecode (that's why we need to // force a safepoint) // + Target thread will not enter any new monitors // void JavaThread::java_suspend() { ! ThreadsListHandle tlh; ! if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) { return; } { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag); if (!is_external_suspend()) { // a racing resume has cancelled us; bail out now return;
*** 2325,2342 **** #ifdef ASSERT // verify the JavaThread has not yet been published in the Threads::list, and // hence doesn't need protection from concurrent access at this stage void JavaThread::verify_not_published() { ! if (!Threads_lock->owned_by_self()) { ! MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); ! assert(!Threads::includes(this), ! "java thread shouldn't have been published yet!"); ! } else { ! assert(!Threads::includes(this), ! "java thread shouldn't have been published yet!"); ! } } #endif // Slow path when the native==>VM/Java barriers detect a safepoint is in // progress or when _suspend_flags is non-zero. --- 2440,2451 ---- #ifdef ASSERT // verify the JavaThread has not yet been published in the Threads::list, and // hence doesn't need protection from concurrent access at this stage void JavaThread::verify_not_published() { ! ThreadsListHandle tlh; ! assert(!tlh.includes(this), "JavaThread shouldn't have been published yet!"); } #endif // Slow path when the native==>VM/Java barriers detect a safepoint is in // progress or when _suspend_flags is non-zero.
*** 2449,2459 **** void JavaThread::java_resume() { assert_locked_or_safepoint(Threads_lock); // Sanity check: thread is gone, has started exiting or the thread // was not externally suspended. ! if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) { return; } MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag); --- 2558,2569 ---- void JavaThread::java_resume() { assert_locked_or_safepoint(Threads_lock); // Sanity check: thread is gone, has started exiting or the thread // was not externally suspended. ! ThreadsListHandle tlh; ! if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) { return; } MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
*** 2917,2926 **** --- 3027,3043 ---- st->print(", id=%d", osthread()->thread_id()); } st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")", p2i(stack_end()), p2i(stack_base())); st->print("]"); + + if (_threads_hazard_ptr != NULL) { + st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr)); + } + if (_nested_threads_hazard_ptr != NULL) { + print_nested_threads_hazard_ptrs_on(st); + } return; } // Verification
*** 3310,3336 **** // ======= Threads ======== // The Threads class links together all active threads, and provides ! // operations over all threads. It is protected by its own Mutex ! // lock, which is also used in other contexts to protect thread ! // operations from having the thread being operated on from exiting ! // and going away unexpectedly (e.g., safepoint synchronization) JavaThread* Threads::_thread_list = NULL; int Threads::_number_of_threads = 0; int Threads::_number_of_non_daemon_threads = 0; int Threads::_return_code = 0; int Threads::_thread_claim_parity = 0; size_t JavaThread::_stack_size_at_create = 0; #ifdef ASSERT bool Threads::_vm_complete = false; #endif // All JavaThreads ! #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next()) // All JavaThreads + all non-JavaThreads (i.e., every thread in the system) void Threads::threads_do(ThreadClosure* tc) { assert_locked_or_safepoint(Threads_lock); // ALL_JAVA_THREADS iterates through all JavaThreads --- 3427,3566 ---- // ======= Threads ======== // The Threads class links together all active threads, and provides ! // operations over all threads. It is protected by the Threads_lock, ! // which is also used in other global contexts like safepointing. ! // ThreadsListHandles are used to safely perform operations on one ! // or more threads without the risk of the thread exiting during the ! // operation. ! // ! // Note: The Threads_lock is currently more widely used than we ! // would like. We are actively migrating Threads_lock uses to other ! // mechanisms in order to reduce Threads_lock contention. JavaThread* Threads::_thread_list = NULL; int Threads::_number_of_threads = 0; int Threads::_number_of_non_daemon_threads = 0; int Threads::_return_code = 0; int Threads::_thread_claim_parity = 0; size_t JavaThread::_stack_size_at_create = 0; + // Safe Memory Reclamation (SMR) support: + Monitor* Threads::_smr_delete_lock = + new Monitor(Monitor::special, "smr_delete_lock", + false /* allow_vm_block */, + Monitor::_safepoint_check_never); + // The '_cnt', '_max' and '_times" fields are enabled via + // -XX:+EnableThreadSMRStatistics: + + // # of parallel threads in _smr_delete_lock->wait(). + // Impl note: Hard to imagine > 64K waiting threads so this could be 16-bit, + // but there is no nice 16-bit _FORMAT support. + uint Threads::_smr_delete_lock_wait_cnt = 0; + + // Max # of parallel threads in _smr_delete_lock->wait(). + // Impl note: See _smr_delete_lock_wait_cnt note. + uint Threads::_smr_delete_lock_wait_max = 0; + + // Flag to indicate when an _smr_delete_lock->notify() is needed. + // Impl note: See _smr_delete_lock_wait_cnt note. + volatile uint Threads::_smr_delete_notify = 0; + + // # of threads deleted over VM lifetime. + // Impl note: Atomically incremented over VM lifetime so use unsigned for more + // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc + // isn't available everywhere (or is it?). + volatile uint Threads::_smr_deleted_thread_cnt = 0; + + // Max time in millis to delete a thread. + // Impl note: 16-bit might be too small on an overloaded machine. Use + // unsigned since this is a time value. Set via Atomic::cmpxchg() in a + // loop for correctness. + volatile uint Threads::_smr_deleted_thread_time_max = 0; + + // Cumulative time in millis to delete threads. + // Impl note: Atomically added to over VM lifetime so use unsigned for more + // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc + // isn't available everywhere (or is it?). + volatile uint Threads::_smr_deleted_thread_times = 0; + + ThreadsList* volatile Threads::_smr_java_thread_list = new ThreadsList(0); + + // # of ThreadsLists allocated over VM lifetime. + // Impl note: We allocate a new ThreadsList for every thread create and + // every thread delete so we need a bigger type than the + // _smr_deleted_thread_cnt field. + uint64_t Threads::_smr_java_thread_list_alloc_cnt = 1; + + // # of ThreadsLists freed over VM lifetime. + // Impl note: See _smr_java_thread_list_alloc_cnt note. + uint64_t Threads::_smr_java_thread_list_free_cnt = 0; + + // Max size ThreadsList allocated. + // Impl note: Max # of threads alive at one time should fit in unsigned 32-bit. + uint Threads::_smr_java_thread_list_max = 0; + + // Max # of nested ThreadsLists for a thread. + // Impl note: Hard to imagine > 64K nested ThreadsLists so this could be + // 16-bit, but there is no nice 16-bit _FORMAT support. + uint Threads::_smr_nested_thread_list_max = 0; + + // # of ThreadsListHandles deleted over VM lifetime. + // Impl note: Atomically incremented over VM lifetime so use unsigned for + // more range. There will be fewer ThreadsListHandles than threads so + // unsigned 32-bit should be fine. + volatile uint Threads::_smr_tlh_cnt = 0; + + // Max time in millis to delete a ThreadsListHandle. + // Impl note: 16-bit might be too small on an overloaded machine. Use + // unsigned since this is a time value. Set via Atomic::cmpxchg() in a + // loop for correctness. + volatile uint Threads::_smr_tlh_time_max = 0; + + // Cumulative time in millis to delete ThreadsListHandles. + // Impl note: Atomically added to over VM lifetime so use unsigned for more + // range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc + // isn't available everywhere (or is it?). + volatile uint Threads::_smr_tlh_times = 0; + + ThreadsList* Threads::_smr_to_delete_list = NULL; + + // # of parallel ThreadsLists on the to-delete list. + // Impl note: Hard to imagine > 64K ThreadsLists needing to be deleted so + // this could be 16-bit, but there is no nice 16-bit _FORMAT support. + uint Threads::_smr_to_delete_list_cnt = 0; + + // Max # of parallel ThreadsLists on the to-delete list. + // Impl note: See _smr_to_delete_list_cnt note. + uint Threads::_smr_to_delete_list_max = 0; + #ifdef ASSERT bool Threads::_vm_complete = false; #endif + static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) { + Prefetch::read((void*)addr, prefetch_interval); + return *addr; + } + + // Possibly the ugliest for loop the world has seen. C++ does not allow + // multiple types in the declaration section of the for loop. In this case + // we are only dealing with pointers and hence can cast them. It looks ugly + // but macros are ugly and therefore it's fine to make things absurdly ugly. + #define DO_JAVA_THREADS(LIST, X) \ + for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes, \ + *MACRO_list = (JavaThread*)(LIST), \ + **MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(), \ + **MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(), \ + *X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval); \ + MACRO_current_p != MACRO_end; \ + MACRO_current_p++, \ + X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval)) + // All JavaThreads ! #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(get_smr_java_thread_list(), X) // All JavaThreads + all non-JavaThreads (i.e., every thread in the system) void Threads::threads_do(ThreadClosure* tc) { assert_locked_or_safepoint(Threads_lock); // ALL_JAVA_THREADS iterates through all JavaThreads
*** 3427,3436 **** --- 3657,3874 ---- JavaValue result(T_VOID); JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(), vmSymbols::void_method_signature(), CHECK); } + // Safe Memory Reclamation (SMR) support: + // + + // Acquire a stable ThreadsList. + // + ThreadsList *Threads::acquire_stable_list(Thread *self, bool is_ThreadsListSetter) { + assert(self != NULL, "sanity check"); + // acquire_stable_list_nested_path() will grab the Threads_lock + // so let's make sure the ThreadsListHandle is in a safe place. + // ThreadsListSetter cannot make this check on this code path. + debug_only(if (!is_ThreadsListSetter && StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);) + + if (self->get_threads_hazard_ptr() == NULL) { + // The typical case is first. + return acquire_stable_list_fast_path(self); + } + + // The nested case is rare. + return acquire_stable_list_nested_path(self); + } + + // Fast path (and lock free) way to acquire a stable ThreadsList. + // + ThreadsList *Threads::acquire_stable_list_fast_path(Thread *self) { + assert(self != NULL, "sanity check"); + assert(self->get_threads_hazard_ptr() == NULL, "sanity check"); + assert(self->get_nested_threads_hazard_ptr() == NULL, + "cannot have a nested hazard ptr with a NULL regular hazard ptr"); + + ThreadsList* threads; + + // Stable recording of a hazard ptr for SMR. This code does not use + // locks so its use of the _smr_java_thread_list & _threads_hazard_ptr + // fields is racy relative to code that uses those fields with locks. + // OrderAccess and Atomic functions are used to deal with those races. + // + while (true) { + threads = get_smr_java_thread_list(); + + // Publish a tagged hazard ptr to denote that the hazard ptr is not + // yet verified as being stable. Due to the fence after the hazard + // ptr write, it will be sequentially consistent w.r.t. the + // sequentially consistent writes of the ThreadsList, even on + // non-multiple copy atomic machines where stores can be observed + // in different order from different observer threads. + ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads); + self->set_threads_hazard_ptr(unverified_threads); + + // If _smr_java_thread_list has changed, we have lost a race with + // Threads::add() or Threads::remove() and have to try again. + if (get_smr_java_thread_list() != threads) { + continue; + } + + // We try to remove the tag which will verify the hazard ptr as + // being stable. This exchange can race with a scanning thread + // which might invalidate the tagged hazard ptr to keep it from + // being followed to access JavaThread ptrs. If we lose the race, + // we simply retry. If we win the race, then the stable hazard + // ptr is officially published. + if (self->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) { + break; + } + } + + // A stable hazard ptr has been published letting other threads know + // that the ThreadsList and the JavaThreads reachable from this list + // are protected and hence they should not be deleted until everyone + // agrees it is safe to do so. + + return threads; + } + + // Acquire a nested stable ThreadsList; this is rare so it uses + // Threads_lock. + // + ThreadsList *Threads::acquire_stable_list_nested_path(Thread *self) { + assert(self != NULL, "sanity check"); + assert(self->get_threads_hazard_ptr() != NULL, + "cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr"); + + // The thread already has a hazard ptr (ThreadsList ref) so we need + // to create a nested ThreadsListHandle with the current ThreadsList + // since it might be different than our current hazard ptr. The need + // for a nested ThreadsListHandle is rare so we do this while holding + // the Threads_lock so we don't race with the scanning code; the code + // is so much simpler this way. + + NestedThreadsList* node; + { + // Only grab the Threads_lock if we don't already own it. + MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock); + node = new NestedThreadsList(get_smr_java_thread_list()); + // We insert at the front of the list to match up with the delete + // in release_stable_list(). + node->set_next(self->get_nested_threads_hazard_ptr()); + self->set_nested_threads_hazard_ptr(node); + if (EnableThreadSMRStatistics) { + self->inc_nested_threads_hazard_ptr_cnt(); + if (self->nested_threads_hazard_ptr_cnt() > _smr_nested_thread_list_max) { + _smr_nested_thread_list_max = self->nested_threads_hazard_ptr_cnt(); + } + } + } + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::acquire_stable_list: add NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list())); + + return node->t_list(); + } + + // Release a stable ThreadsList. + // + void Threads::release_stable_list(Thread *self) { + assert(self != NULL, "sanity check"); + // release_stable_list_nested_path() will grab the Threads_lock + // so let's make sure the ThreadsListHandle is in a safe place. + debug_only(if (StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);) + + if (self->get_nested_threads_hazard_ptr() == NULL) { + // The typical case is first. + release_stable_list_fast_path(self); + return; + } + + // The nested case is rare. + release_stable_list_nested_path(self); + } + + // Fast path way to release a stable ThreadsList. The release portion + // is lock-free, but the wake up portion is not. + // + void Threads::release_stable_list_fast_path(Thread *self) { + assert(self != NULL, "sanity check"); + assert(self->get_threads_hazard_ptr() != NULL, "sanity check"); + assert(self->get_nested_threads_hazard_ptr() == NULL, + "cannot have a nested hazard ptr when releasing a regular hazard ptr"); + + // After releasing the hazard ptr, other threads may go ahead and + // free up some memory temporarily used by a ThreadsList snapshot. + self->set_threads_hazard_ptr(NULL); + + // We use double-check locking to reduce traffic on the system + // wide smr_delete_lock. + if (Threads::smr_delete_notify()) { + // An exiting thread might be waiting in smr_delete(); we need to + // check with smr_delete_lock to be sure. + release_stable_list_wake_up((char *) "regular hazard ptr"); + } + } + + // Release a nested stable ThreadsList; this is rare so it uses + // Threads_lock. + // + void Threads::release_stable_list_nested_path(Thread *self) { + assert(self != NULL, "sanity check"); + assert(self->get_nested_threads_hazard_ptr() != NULL, "sanity check"); + assert(self->get_threads_hazard_ptr() != NULL, + "must have a regular hazard ptr to have nested hazard ptrs"); + + // We have a nested ThreadsListHandle so we have to release it first. + // The need for a nested ThreadsListHandle is rare so we do this while + // holding the Threads_lock so we don't race with the scanning code; + // the code is so much simpler this way. + + NestedThreadsList *node; + { + // Only grab the Threads_lock if we don't already own it. + MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock); + // We remove from the front of the list to match up with the insert + // in acquire_stable_list(). + node = self->get_nested_threads_hazard_ptr(); + self->set_nested_threads_hazard_ptr(node->next()); + if (EnableThreadSMRStatistics) { + self->dec_nested_threads_hazard_ptr_cnt(); + } + } + + // An exiting thread might be waiting in smr_delete(); we need to + // check with smr_delete_lock to be sure. + release_stable_list_wake_up((char *) "nested hazard ptr"); + + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list: delete NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list())); + + delete node; + } + + // Wake up portion of the release stable ThreadsList protocol; + // uses the smr_delete_lock(). + // + void Threads::release_stable_list_wake_up(char *log_str) { + assert(log_str != NULL, "sanity check"); + + // Note: smr_delete_lock is held in smr_delete() for the entire + // hazard ptr search so that we do not lose this notify() if + // the exiting thread has to wait. That code path also holds + // Threads_lock (which was grabbed before smr_delete_lock) so that + // threads_do() can be called. This means the system can't start a + // safepoint which means this thread can't take too long to get to + // a safepoint because of being blocked on smr_delete_lock. + // + MonitorLockerEx ml(Threads::smr_delete_lock(), Monitor::_no_safepoint_check_flag); + if (Threads::smr_delete_notify()) { + // Notify any exiting JavaThreads that are waiting in smr_delete() + // that we've released a ThreadsList. + ml.notify_all(); + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list notified %s", os::current_thread_id(), log_str); + } + } + void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) { TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime)); if (EagerXrunInit && Arguments::init_libraries_at_startup()) { create_vm_init_libraries();
*** 3608,3618 **** main_thread->set_active_handles(JNIHandleBlock::allocate_block()); if (!main_thread->set_as_starting_thread()) { vm_shutdown_during_initialization( "Failed necessary internal allocation. Out of swap space"); ! delete main_thread; *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again return JNI_ENOMEM; } // Enable guard page *after* os::create_main_thread(), otherwise it would --- 4046,4056 ---- main_thread->set_active_handles(JNIHandleBlock::allocate_block()); if (!main_thread->set_as_starting_thread()) { vm_shutdown_during_initialization( "Failed necessary internal allocation. Out of swap space"); ! main_thread->smr_delete(); *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again return JNI_ENOMEM; } // Enable guard page *after* os::create_main_thread(), otherwise it would
*** 3623,3633 **** ObjectMonitor::Initialize(); // Initialize global modules jint status = init_globals(); if (status != JNI_OK) { ! delete main_thread; *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again return status; } if (TRACE_INITIALIZE() != JNI_OK) { --- 4061,4071 ---- ObjectMonitor::Initialize(); // Initialize global modules jint status = init_globals(); if (status != JNI_OK) { ! main_thread->smr_delete(); *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again return status; } if (TRACE_INITIALIZE() != JNI_OK) {
*** 4029,4056 **** vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name()); } } } - JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) { - assert(Threads_lock->owned_by_self(), "Must hold Threads_lock"); - JavaThread* java_thread = NULL; - // Sequential search for now. Need to do better optimization later. - for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) { - oop tobj = thread->threadObj(); - if (!thread->is_exiting() && - tobj != NULL && - java_tid == java_lang_Thread::thread_id(tobj)) { - java_thread = thread; - break; - } - } - return java_thread; - } - - // Last thread running calls java.lang.Shutdown.shutdown() void JavaThread::invoke_shutdown_hooks() { HandleMark hm(this); // We could get here with a pending exception, if so clear it now. --- 4467,4477 ----
*** 4171,4180 **** --- 4592,4606 ---- VM_Exit::set_vm_exited(); notify_vm_shutdown(); + // We are after VM_Exit::set_vm_exited() so we can't call + // thread->smr_delete() or we will block on the Threads_lock. + // Deleting the shutdown thread here is safe because another + // JavaThread cannot have an active ThreadsListHandle for + // this JavaThread. delete thread; #if INCLUDE_JVMCI if (JVMCICounterSize > 0) { FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
*** 4204,4223 **** --- 4630,5148 ---- if (version == JNI_VERSION_9) return JNI_TRUE; if (version == JNI_VERSION_10) return JNI_TRUE; return JNI_FALSE; } + // Hash table of pointers found by a scan. Used for collecting hazard + // pointers (ThreadsList references). Also used for collecting JavaThreads + // that are indirectly referenced by hazard ptrs. An instance of this + // class only contains one type of pointer. + // + class ThreadScanHashtable : public CHeapObj<mtThread> { + private: + static bool ptr_equals(void * const& s1, void * const& s2) { + return s1 == s2; + } + static unsigned int ptr_hash(void * const& s1) { + return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u); + } + + int _table_size; + // ResourceHashtable SIZE is specified at compile time so our + // dynamic _table_size is unused for now; 1031 is the first prime + // after 1024. + typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash, + &ThreadScanHashtable::ptr_equals, 1031, + ResourceObj::C_HEAP, mtThread> PtrTable; + PtrTable * _ptrs; + + public: + // ResourceHashtable is passed to various functions and populated in + // different places so we allocate it using C_HEAP to make it immune + // from any ResourceMarks that happen to be in the code paths. + ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {} + + ~ThreadScanHashtable() { delete _ptrs; } + + bool has_entry(void *pointer) { + int *val_ptr = _ptrs->get(pointer); + return val_ptr != NULL && *val_ptr == 1; + } + + void add_entry(void *pointer) { + _ptrs->put(pointer, 1); + } + }; + + // Closure to gather JavaThreads indirectly referenced by hazard ptrs + // (ThreadsList references) into a hash table. This closure handles part 2 + // of the dance - adding all the JavaThreads referenced by the hazard + // pointer (ThreadsList reference) to the hash table. + // + class AddThreadHazardPointerThreadClosure : public ThreadClosure { + private: + ThreadScanHashtable *_table; + + public: + AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {} + + virtual void do_thread(Thread *thread) { + if (!_table->has_entry((void*)thread)) { + // The same JavaThread might be on more than one ThreadsList or + // more than one thread might be using the same ThreadsList. In + // either case, we only need a single entry for a JavaThread. + _table->add_entry((void*)thread); + } + } + }; + + // Closure to gather JavaThreads indirectly referenced by hazard ptrs + // (ThreadsList references) into a hash table. This closure handles part 1 + // of the dance - hazard ptr chain walking and dispatch to another + // closure. + // + class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure { + private: + ThreadScanHashtable *_table; + public: + ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {} + + virtual void do_thread(Thread *thread) { + assert_locked_or_safepoint(Threads_lock); + + if (thread == NULL) return; + + // This code races with Threads::acquire_stable_list() which is + // lock-free so we have to handle some special situations. + // + ThreadsList *current_list = NULL; + while (true) { + current_list = thread->get_threads_hazard_ptr(); + // No hazard ptr so nothing more to do. + if (current_list == NULL) { + assert(thread->get_nested_threads_hazard_ptr() == NULL, + "cannot have a nested hazard ptr with a NULL regular hazard ptr"); + return; + } + + // If the hazard ptr is verified as stable (since it is not tagged), + // then it is safe to use. + if (!Thread::is_hazard_ptr_tagged(current_list)) break; + + // The hazard ptr is tagged as not yet verified as being stable + // so we are racing with acquire_stable_list(). This exchange + // attempts to invalidate the hazard ptr. If we win the race, + // then we can ignore this unstable hazard ptr and the other + // thread will retry the attempt to publish a stable hazard ptr. + // If we lose the race, then we retry our attempt to look at the + // hazard ptr. + if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return; + } + + // The current JavaThread has a hazard ptr (ThreadsList reference) + // which might be _smr_java_thread_list or it might be an older + // ThreadsList that has been removed but not freed. In either case, + // the hazard ptr is protecting all the JavaThreads on that + // ThreadsList. + AddThreadHazardPointerThreadClosure add_cl(_table); + current_list->threads_do(&add_cl); + + // Any NestedThreadsLists are also protecting JavaThreads so + // gather those also; the ThreadsLists may be different. + for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr(); + node != NULL; node = node->next()) { + node->t_list()->threads_do(&add_cl); + } + } + }; + + // Closure to print JavaThreads that have a hazard ptr (ThreadsList + // reference) that contains an indirect reference to a specific JavaThread. + // + class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure { + private: + JavaThread *_thread; + public: + ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {} + + virtual void do_thread(Thread *thread) { + assert_locked_or_safepoint(Threads_lock); + + if (thread == NULL) return; + ThreadsList *current_list = thread->get_threads_hazard_ptr(); + if (current_list == NULL) { + assert(thread->get_nested_threads_hazard_ptr() == NULL, + "cannot have a nested hazard ptr with a NULL regular hazard ptr"); + return; + } + // If the hazard ptr is unverified, then ignore it. + if (Thread::is_hazard_ptr_tagged(current_list)) return; + + // The current JavaThread has a hazard ptr (ThreadsList reference) + // which might be _smr_java_thread_list or it might be an older + // ThreadsList that has been removed but not freed. In either case, + // the hazard ptr is protecting all the JavaThreads on that + // ThreadsList, but we only care about matching a specific JavaThread. + DO_JAVA_THREADS(current_list, p) { + if (p == _thread) { + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread)); + break; + } + } + + // Any NestedThreadsLists are also protecting JavaThreads so + // check those also; the ThreadsLists may be different. + for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr(); + node != NULL; node = node->next()) { + DO_JAVA_THREADS(node->t_list(), p) { + if (p == _thread) { + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a nested hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread)); + return; + } + } + } + } + }; + + // Return true if the specified JavaThread is protected by a hazard + // pointer (ThreadsList reference). Otherwise, returns false. + // + bool Threads::is_a_protected_JavaThread(JavaThread *thread) { + assert_locked_or_safepoint(Threads_lock); + + // Hash table size should be first power of two higher than twice + // the length of the Threads list. + int hash_table_size = MIN2(_number_of_threads, 32) << 1; + hash_table_size--; + hash_table_size |= hash_table_size >> 1; + hash_table_size |= hash_table_size >> 2; + hash_table_size |= hash_table_size >> 4; + hash_table_size |= hash_table_size >> 8; + hash_table_size |= hash_table_size >> 16; + hash_table_size++; + + // Gather a hash table of the JavaThreads indirectly referenced by + // hazard ptrs. + ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); + ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table); + Threads::threads_do(&scan_cl); + + bool thread_is_protected = false; + if (scan_table->has_entry((void*)thread)) { + thread_is_protected = true; + } + delete scan_table; + return thread_is_protected; + } + + // Safely delete a JavaThread when it is no longer in use by a + // ThreadsListHandle. + // + void Threads::smr_delete(JavaThread *thread) { + assert(!Threads_lock->owned_by_self(), "sanity"); + + bool has_logged_once = false; + elapsedTimer timer; + if (EnableThreadSMRStatistics) { + timer.start(); + } + + while (true) { + { + // No safepoint check because this JavaThread is not on the + // Threads list. + MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); + // Cannot use a MonitorLockerEx helper here because we have + // to drop the Threads_lock first if we wait. + Threads::smr_delete_lock()->lock_without_safepoint_check(); + // Set the smr_delete_notify flag after we grab smr_delete_lock + // and before we scan hazard ptrs because we're doing + // double-check locking in release_stable_list(). + Threads::set_smr_delete_notify(); + + if (!is_a_protected_JavaThread(thread)) { + // This is the common case. + Threads::clear_smr_delete_notify(); + Threads::smr_delete_lock()->unlock(); + break; + } + if (!has_logged_once) { + has_logged_once = true; + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread)); + if (log_is_enabled(Debug, os, thread)) { + ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread); + Threads::threads_do(&scan_cl); + } + } + } // We have to drop the Threads_lock to wait or delete the thread + + if (EnableThreadSMRStatistics) { + _smr_delete_lock_wait_cnt++; + if (_smr_delete_lock_wait_cnt > _smr_delete_lock_wait_max) { + _smr_delete_lock_wait_max = _smr_delete_lock_wait_cnt; + } + } + // Wait for a release_stable_list() call before we check again. No + // safepoint check, no timeout, and not as suspend equivalent flag + // because this JavaThread is not on the Threads list. + Threads::smr_delete_lock()->wait(Mutex::_no_safepoint_check_flag, 0, + !Mutex::_as_suspend_equivalent_flag); + if (EnableThreadSMRStatistics) { + _smr_delete_lock_wait_cnt--; + } + + Threads::clear_smr_delete_notify(); + Threads::smr_delete_lock()->unlock(); + // Retry the whole scenario. + } + + if (ThreadLocalHandshakes) { + // The thread is about to be deleted so cancel any handshake. + thread->cancel_handshake(); + } + + delete thread; + if (EnableThreadSMRStatistics) { + timer.stop(); + uint millis = (uint)timer.milliseconds(); + Threads::inc_smr_deleted_thread_cnt(); + Threads::add_smr_deleted_thread_times(millis); + Threads::update_smr_deleted_thread_time_max(millis); + } + + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread)); + } + + bool Threads::smr_delete_notify() { + // Use load_acquire() in order to see any updates to _smr_delete_notify + // earlier than when smr_delete_lock is grabbed. + return (OrderAccess::load_acquire(&_smr_delete_notify) != 0); + } + + // set_smr_delete_notify() and clear_smr_delete_notify() are called + // under the protection of the smr_delete_lock, but we also use an + // Atomic operation to ensure the memory update is seen earlier than + // when the smr_delete_lock is dropped. + // + void Threads::set_smr_delete_notify() { + Atomic::inc(&_smr_delete_notify); + } + + void Threads::clear_smr_delete_notify() { + Atomic::dec(&_smr_delete_notify); + } + + // Closure to gather hazard ptrs (ThreadsList references) into a hash table. + // + class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure { + private: + ThreadScanHashtable *_table; + public: + ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {} + + virtual void do_thread(Thread* thread) { + assert_locked_or_safepoint(Threads_lock); + + if (thread == NULL) return; + ThreadsList *threads = thread->get_threads_hazard_ptr(); + if (threads == NULL) { + assert(thread->get_nested_threads_hazard_ptr() == NULL, + "cannot have a nested hazard ptr with a NULL regular hazard ptr"); + return; + } + // In this closure we always ignore the tag that might mark this + // hazard ptr as not yet verified. If we happen to catch an + // unverified hazard ptr that is subsequently discarded (not + // published), then the only side effect is that we might keep a + // to-be-deleted ThreadsList alive a little longer. + threads = Thread::untag_hazard_ptr(threads); + if (!_table->has_entry((void*)threads)) { + _table->add_entry((void*)threads); + } + + // Any NestedThreadsLists are also protecting JavaThreads so + // gather those also; the ThreadsLists may be different. + for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr(); + node != NULL; node = node->next()) { + threads = node->t_list(); + if (!_table->has_entry((void*)threads)) { + _table->add_entry((void*)threads); + } + } + } + }; + + // Safely free a ThreadsList after a Threads::add() or Threads::remove(). + // The specified ThreadsList may not get deleted during this call if it + // is still in-use (referenced by a hazard ptr). Other ThreadsLists + // in the chain may get deleted by this call if they are no longer in-use. + void Threads::smr_free_list(ThreadsList* threads) { + assert_locked_or_safepoint(Threads_lock); + + threads->set_next_list(_smr_to_delete_list); + _smr_to_delete_list = threads; + if (EnableThreadSMRStatistics) { + _smr_to_delete_list_cnt++; + if (_smr_to_delete_list_cnt > _smr_to_delete_list_max) { + _smr_to_delete_list_max = _smr_to_delete_list_cnt; + } + } + + // Hash table size should be first power of two higher than twice the length of the ThreadsList + int hash_table_size = MIN2(_number_of_threads, 32) << 1; + hash_table_size--; + hash_table_size |= hash_table_size >> 1; + hash_table_size |= hash_table_size >> 2; + hash_table_size |= hash_table_size >> 4; + hash_table_size |= hash_table_size >> 8; + hash_table_size |= hash_table_size >> 16; + hash_table_size++; + + // Gather a hash table of the current hazard ptrs: + ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size); + ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table); + Threads::threads_do(&scan_cl); + + // Walk through the linked list of pending freeable ThreadsLists + // and free the ones that are not referenced from hazard ptrs. + ThreadsList* current = _smr_to_delete_list; + ThreadsList* prev = NULL; + ThreadsList* next = NULL; + bool threads_is_freed = false; + while (current != NULL) { + next = current->next_list(); + if (!scan_table->has_entry((void*)current)) { + // This ThreadsList is not referenced by a hazard ptr. + if (prev != NULL) { + prev->set_next_list(next); + } + if (_smr_to_delete_list == current) { + _smr_to_delete_list = next; + } + + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current)); + if (current == threads) threads_is_freed = true; + delete current; + if (EnableThreadSMRStatistics) { + _smr_java_thread_list_free_cnt++; + _smr_to_delete_list_cnt--; + } + } else { + prev = current; + } + current = next; + } + + if (!threads_is_freed) { + // Only report "is not freed" on the original call to + // smr_free_list() for this ThreadsList. + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads)); + } + + delete scan_table; + } + + // Remove a JavaThread from a ThreadsList. The returned ThreadsList is a + // new copy of the specified ThreadsList with the specified JavaThread + // removed. + ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) { + assert(list->_length > 0, "sanity"); + + uint i = 0; + DO_JAVA_THREADS(list, current) { + if (current == java_thread) { + break; + } + i++; + } + assert(i < list->_length, "did not find JavaThread on the list"); + const uint index = i; + const uint new_length = list->_length - 1; + const uint head_length = index; + const uint tail_length = (new_length >= index) ? (new_length - index) : 0; + ThreadsList *const new_list = new ThreadsList(new_length); + + if (head_length > 0) { + Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); + } + if (tail_length > 0) { + Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length); + } + + return new_list; + } + + // Add a JavaThread to a ThreadsList. The returned ThreadsList is a + // new copy of the specified ThreadsList with the specified JavaThread + // appended to the end. + ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) { + const uint index = list->_length; + const uint new_length = index + 1; + const uint head_length = index; + ThreadsList *const new_list = new ThreadsList(new_length); + + if (head_length > 0) { + Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length); + } + *(JavaThread**)(new_list->_threads + index) = java_thread; + + return new_list; + } + + int ThreadsList::find_index_of_JavaThread(JavaThread *target) { + if (target == NULL) { + return -1; + } + for (uint i = 0; i < length(); i++) { + if (target == thread_at(i)) { + return (int)i; + } + } + return -1; + } + + JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const { + DO_JAVA_THREADS(this, thread) { + oop tobj = thread->threadObj(); + // Ignore the thread if it hasn't run yet, has exited + // or is starting to exit. + if (tobj != NULL && !thread->is_exiting() && + java_tid == java_lang_Thread::thread_id(tobj)) { + // found a match + return thread; + } + } + return NULL; + } + + bool ThreadsList::includes(const JavaThread * const p) const { + if (p == NULL) { + return false; + } + DO_JAVA_THREADS(this, q) { + if (q == p) { + return true; + } + } + return false; + } + void Threads::add(JavaThread* p, bool force_daemon) { // The threads lock must be owned at this point assert_locked_or_safepoint(Threads_lock); // See the comment for this method in thread.hpp for its purpose and // why it is called here. p->initialize_queues(); p->set_next(_thread_list); _thread_list = p; + + // Once a JavaThread is added to the Threads list, smr_delete() has + // to be used to delete it. Otherwise we can just delete it directly. + p->set_on_thread_list(); + _number_of_threads++; oop threadObj = p->threadObj(); bool daemon = true; // Bootstrapping problem: threadObj can be null for initial // JavaThread (or for threads attached via JNI)
*** 4226,4235 **** --- 5151,5174 ---- daemon = false; } ThreadService::add_thread(p, daemon); + // Maintain fast thread list + ThreadsList *new_list = ThreadsList::add_thread(get_smr_java_thread_list(), p); + if (EnableThreadSMRStatistics) { + _smr_java_thread_list_alloc_cnt++; + if (new_list->length() > _smr_java_thread_list_max) { + _smr_java_thread_list_max = new_list->length(); + } + } + // Initial _smr_java_thread_list will not generate a "Threads::add" mesg. + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); + + ThreadsList *old_list = xchg_smr_java_thread_list(new_list); + smr_free_list(old_list); + // Possible GC point. Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p)); } void Threads::remove(JavaThread* p) {
*** 4239,4250 **** // Extra scope needed for Thread_lock, so we can check // that we do not remove thread without safepoint code notice { MutexLocker ml(Threads_lock); ! assert(includes(p), "p must be present"); JavaThread* current = _thread_list; JavaThread* prev = NULL; while (current != p) { prev = current; --- 5178,5202 ---- // Extra scope needed for Thread_lock, so we can check // that we do not remove thread without safepoint code notice { MutexLocker ml(Threads_lock); ! assert(get_smr_java_thread_list()->includes(p), "p must be present"); + // Maintain fast thread list + ThreadsList *new_list = ThreadsList::remove_thread(get_smr_java_thread_list(), p); + if (EnableThreadSMRStatistics) { + _smr_java_thread_list_alloc_cnt++; + // This list is smaller so no need to check for a "longest" update. + } + + // Final _smr_java_thread_list will not generate a "Threads::remove" mesg. + log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list)); + + ThreadsList *old_list = xchg_smr_java_thread_list(new_list); + smr_free_list(old_list); + JavaThread* current = _thread_list; JavaThread* prev = NULL; while (current != p) { prev = current;
*** 4254,4263 **** --- 5206,5216 ---- if (prev) { prev->set_next(current->next()); } else { _thread_list = p->next(); } + _number_of_threads--; oop threadObj = p->threadObj(); bool daemon = true; if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) { _number_of_non_daemon_threads--;
*** 4280,4300 **** // Since Events::log uses a lock, we grab it outside the Threads_lock Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p)); } - // Threads_lock must be held when this is called (or must be called during a safepoint) - bool Threads::includes(JavaThread* p) { - assert(Threads_lock->is_locked(), "sanity check"); - ALL_JAVA_THREADS(q) { - if (q == p) { - return true; - } - } - return false; - } - // Operations on the Threads list for GC. These are not explicitly locked, // but the garbage collector must provide a safe context for them to run. // In particular, these things should never be called when the Threads_lock // is held by some other thread. (Note: the Safepoint abstraction also // uses the Threads_lock to guarantee this property. It also makes sure that --- 5233,5242 ----
*** 4403,4453 **** } } // Get count Java threads that are waiting to enter the specified monitor. ! GrowableArray<JavaThread*>* Threads::get_pending_threads(int count, ! address monitor, ! bool doLock) { ! assert(doLock || SafepointSynchronize::is_at_safepoint(), ! "must grab Threads_lock or be at safepoint"); GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count); int i = 0; ! { ! MutexLockerEx ml(doLock ? Threads_lock : NULL); ! ALL_JAVA_THREADS(p) { if (!p->can_call_java()) continue; address pending = (address)p->current_pending_monitor(); if (pending == monitor) { // found a match if (i < count) result->append(p); // save the first count matches i++; } } ! } return result; } ! JavaThread *Threads::owning_thread_from_monitor_owner(address owner, ! bool doLock) { ! assert(doLock || ! Threads_lock->owned_by_self() || ! SafepointSynchronize::is_at_safepoint(), ! "must grab Threads_lock or be at safepoint"); ! // NULL owner means not locked so we can skip the search if (owner == NULL) return NULL; ! { ! MutexLockerEx ml(doLock ? Threads_lock : NULL); ! ALL_JAVA_THREADS(p) { // first, see if owner is the address of a Java thread if (owner == (address)p) return p; } ! } // Cannot assert on lack of success here since this function may be // used by code that is trying to report useful problem information // like deadlock detection. if (UseHeavyMonitors) return NULL; --- 5345,5384 ---- } } // Get count Java threads that are waiting to enter the specified monitor. ! GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list, ! int count, ! address monitor) { GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count); int i = 0; ! DO_JAVA_THREADS(t_list, p) { if (!p->can_call_java()) continue; address pending = (address)p->current_pending_monitor(); if (pending == monitor) { // found a match if (i < count) result->append(p); // save the first count matches i++; } } ! return result; } ! JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list, ! address owner) { // NULL owner means not locked so we can skip the search if (owner == NULL) return NULL; ! DO_JAVA_THREADS(t_list, p) { // first, see if owner is the address of a Java thread if (owner == (address)p) return p; } ! // Cannot assert on lack of success here since this function may be // used by code that is trying to report useful problem information // like deadlock detection. if (UseHeavyMonitors) return NULL;
*** 4454,4472 **** // If we didn't find a matching Java thread and we didn't force use of // heavyweight monitors, then the owner is the stack address of the // Lock Word in the owning Java thread's stack. // JavaThread* the_owner = NULL; ! { ! MutexLockerEx ml(doLock ? Threads_lock : NULL); ! ALL_JAVA_THREADS(q) { if (q->is_lock_owned(owner)) { the_owner = q; break; } } ! } // cannot assert on lack of success here; see above comment return the_owner; } // Threads::print_on() is called at safepoint by VM_PrintThreads operation. --- 5385,5401 ---- // If we didn't find a matching Java thread and we didn't force use of // heavyweight monitors, then the owner is the stack address of the // Lock Word in the owning Java thread's stack. // JavaThread* the_owner = NULL; ! DO_JAVA_THREADS(t_list, q) { if (q->is_lock_owned(owner)) { the_owner = q; break; } } ! // cannot assert on lack of success here; see above comment return the_owner; } // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
*** 4487,4496 **** --- 5416,5428 ---- if (print_concurrent_locks) { concurrent_locks.dump_at_safepoint(); } #endif // INCLUDE_SERVICES + print_smr_info_on(st); + st->cr(); + ALL_JAVA_THREADS(p) { ResourceMark rm; p->print_on(st); if (print_stacks) { if (internal_format) {
*** 4513,4525 **** --- 5445,5553 ---- WatcherThread* wt = WatcherThread::watcher_thread(); if (wt != NULL) { wt->print_on(st); st->cr(); } + st->flush(); } + // Log Threads class SMR info. + void Threads::log_smr_statistics() { + LogTarget(Info, thread, smr) log; + if (log.is_enabled()) { + LogStream out(log); + print_smr_info_on(&out); + } + } + + // Print Threads class SMR info. + void Threads::print_smr_info_on(outputStream* st) { + // Only grab the Threads_lock if we don't already own it + // and if we are not reporting an error. + MutexLockerEx ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock); + + st->print_cr("Threads class SMR info:"); + st->print_cr("_smr_java_thread_list=" INTPTR_FORMAT ", length=%u, " + "elements={", p2i(_smr_java_thread_list), + _smr_java_thread_list->length()); + print_smr_info_elements_on(st, _smr_java_thread_list); + st->print_cr("}"); + if (_smr_to_delete_list != NULL) { + st->print_cr("_smr_to_delete_list=" INTPTR_FORMAT ", length=%u, " + "elements={", p2i(_smr_to_delete_list), + _smr_to_delete_list->length()); + print_smr_info_elements_on(st, _smr_to_delete_list); + st->print_cr("}"); + for (ThreadsList *t_list = _smr_to_delete_list->next_list(); + t_list != NULL; t_list = t_list->next_list()) { + st->print("next-> " INTPTR_FORMAT ", length=%u, " + "elements={", p2i(t_list), t_list->length()); + print_smr_info_elements_on(st, t_list); + st->print_cr("}"); + } + } + if (!EnableThreadSMRStatistics) { + return; + } + st->print_cr("_smr_java_thread_list_alloc_cnt=" UINT64_FORMAT "," + "_smr_java_thread_list_free_cnt=" UINT64_FORMAT "," + "_smr_java_thread_list_max=%u, " + "_smr_nested_thread_list_max=%u", + _smr_java_thread_list_alloc_cnt, + _smr_java_thread_list_free_cnt, + _smr_java_thread_list_max, + _smr_nested_thread_list_max); + if (_smr_tlh_cnt > 0) { + st->print_cr("_smr_tlh_cnt=%u" + ", _smr_tlh_times=%u" + ", avg_smr_tlh_time=%0.2f" + ", _smr_tlh_time_max=%u", + _smr_tlh_cnt, _smr_tlh_times, + ((double) _smr_tlh_times / _smr_tlh_cnt), + _smr_tlh_time_max); + } + if (_smr_deleted_thread_cnt > 0) { + st->print_cr("_smr_deleted_thread_cnt=%u" + ", _smr_deleted_thread_times=%u" + ", avg_smr_deleted_thread_time=%0.2f" + ", _smr_deleted_thread_time_max=%u", + _smr_deleted_thread_cnt, _smr_deleted_thread_times, + ((double) _smr_deleted_thread_times / _smr_deleted_thread_cnt), + _smr_deleted_thread_time_max); + } + st->print_cr("_smr_delete_lock_wait_cnt=%u, _smr_delete_lock_wait_max=%u", + _smr_delete_lock_wait_cnt, _smr_delete_lock_wait_max); + st->print_cr("_smr_to_delete_list_cnt=%u, _smr_to_delete_list_max=%u", + _smr_to_delete_list_cnt, _smr_to_delete_list_max); + } + + // Print ThreadsList elements (4 per line). + void Threads::print_smr_info_elements_on(outputStream* st, + ThreadsList* t_list) { + uint cnt = 0; + JavaThreadIterator jti(t_list); + for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) { + st->print(INTPTR_FORMAT, p2i(jt)); + if (cnt < t_list->length() - 1) { + // Separate with comma or comma-space except for the last one. + if (((cnt + 1) % 4) == 0) { + // Four INTPTR_FORMAT fit on an 80 column line so end the + // current line with just a comma. + st->print_cr(","); + } else { + // Not the last one on the current line so use comma-space: + st->print(", "); + } + } else { + // Last one so just end the current line. + st->cr(); + } + cnt++; + } + } + void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf, int buflen, bool* found_current) { if (this_thread != NULL) { bool is_current = (current == this_thread); *found_current = *found_current || is_current;
*** 4552,4561 **** --- 5580,5592 ---- // that VM is not at safepoint and/or current thread is inside signal handler. // Don't print stack trace, as the stack may not be walkable. Don't allocate // memory (even in resource area), it might deadlock the error handler. void Threads::print_on_error(outputStream* st, Thread* current, char* buf, int buflen) { + print_smr_info_on(st); + st->cr(); + bool found_current = false; st->print_cr("Java Threads: ( => current thread )"); ALL_JAVA_THREADS(thread) { print_on_error(thread, st, current, buf, buflen, &found_current); }
*** 4573,4582 **** --- 5604,5614 ---- st->print("=>" PTR_FORMAT " (exited) ", p2i(current)); current->print_on_error(st, buf, buflen); st->cr(); } st->cr(); + st->print_cr("Threads with active compile tasks:"); print_threads_compiling(st, buf, buflen); } void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
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