void VM_DeoptimizeAll::doit() {
DeoptimizationMarker dm;
// deoptimize all java threads in the system
if (DeoptimizeALot) {
for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
if (thread->has_last_Java_frame()) {
thread->deoptimize();
}
}
} else if (DeoptimizeRandom) {
// Deoptimize some selected threads and frames
int tnum = os::random() & 0x3;
int fnum = os::random() & 0x3;
int tcount = 0;
for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
if (thread->has_last_Java_frame()) {
if (tcount++ == tnum) {
tcount = 0;
int fcount = 0;
// Deoptimize some selected frames.
// Biased llocking wants a updated register map
for(StackFrameStream fst(thread, UseBiasedLocking); !fst.is_done(); fst.next()) {
if (fst.current()->can_be_deoptimized()) {
if (fcount++ == fnum) {
fcount = 0;
Deoptimization::deoptimize(thread, *fst.current(), fst.register_map());
}
}
}
}
}
}
}
}
void ThreadLocalAllocBuffer::accumulate_statistics_before_gc() {
global_stats()->initialize();
#ifdef COLORED_TLABS
if(UseColoredSpaces) {
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
//tty->print("early: %p\n", thread);
thread->tlab(HC_RED).accumulate_statistics();
thread->tlab(HC_RED).initialize_statistics();
thread->tlab(HC_BLUE).accumulate_statistics();
thread->tlab(HC_BLUE).initialize_statistics();
}
} else {
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
//tty->print("early: %p\n", thread);
thread->tlab().accumulate_statistics();
thread->tlab().initialize_statistics();
}
}
#else
for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
thread->tlab().accumulate_statistics();
thread->tlab().initialize_statistics();
}
#endif
// Publish new stats if some allocation occurred.
if (global_stats()->allocation() != 0) {
global_stats()->publish();
if (PrintTLAB) {
global_stats()->print();
}
}
}
void ThreadLocalAllocBuffer::resize_all_tlabs() {
if (ResizeTLAB) {
if (UseColoredSpaces) {
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
thread->tlab(HC_RED).resize();
thread->tlab(HC_BLUE).resize();
}
} else {
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
thread->tlab().resize();
}
}
}
}
void ThreadLocalAllocBuffer::resize_all_tlabs() {
if (ResizeTLAB) {
for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
thread->tlab().resize();
}
}
}
void DirtyCardQueueSet::concatenate_logs() {
// Iterate over all the threads, if we find a partial log add it to
// the global list of logs. Temporarily turn off the limit on the number
// of outstanding buffers.
int save_max_completed_queue = _max_completed_queue;
_max_completed_queue = max_jint;
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
for (JavaThread* t = Threads::first(); t; t = t->next()) {
DirtyCardQueue& dcq = t->dirty_card_queue();
if (dcq.size() != 0) {
void **buf = t->dirty_card_queue().get_buf();
// We must NULL out the unused entries, then enqueue.
for (size_t i = 0; i < t->dirty_card_queue().get_index(); i += oopSize) {
buf[PtrQueue::byte_index_to_index((int)i)] = NULL;
}
enqueue_complete_buffer(dcq.get_buf(), dcq.get_index());
dcq.reinitialize();
}
}
if (_shared_dirty_card_queue.size() != 0) {
enqueue_complete_buffer(_shared_dirty_card_queue.get_buf(),
_shared_dirty_card_queue.get_index());
_shared_dirty_card_queue.reinitialize();
}
// Restore the completed buffer queue limit.
_max_completed_queue = save_max_completed_queue;
}
void MemProfiler::do_trace() {
// Calculate thread local sizes
size_t handles_memory_usage = VMThread::vm_thread()->handle_area()->size_in_bytes();
size_t resource_memory_usage = VMThread::vm_thread()->resource_area()->size_in_bytes();
JavaThread *cur = Threads::first();
while (cur != NULL) {
handles_memory_usage += cur->handle_area()->size_in_bytes();
resource_memory_usage += cur->resource_area()->size_in_bytes();
cur = cur->next();
}
// Print trace line in log
fprintf(_log_fp, "%6.1f,%5d,%5d," UINTX_FORMAT_W(6) "," UINTX_FORMAT_W(6) ",",
os::elapsedTime(),
Threads::number_of_threads(),
SystemDictionary::number_of_classes(),
Universe::heap()->used() / K,
Universe::heap()->capacity() / K);
fprintf(_log_fp, UINTX_FORMAT_W(6) ",", CodeCache::capacity() / K);
fprintf(_log_fp, UINTX_FORMAT_W(6) "," UINTX_FORMAT_W(6) ",%6ld\n",
handles_memory_usage / K,
resource_memory_usage / K,
OopMapCache::memory_usage() / K);
fflush(_log_fp);
}
void DirtyCardQueueSet::abandon_logs() {
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
clear();
// Since abandon is done only at safepoints, we can safely manipulate
// these queues.
for (JavaThread* t = Threads::first(); t; t = t->next()) {
t->dirty_card_queue().reset();
}
shared_dirty_card_queue()->reset();
}
void VM_ThreadDump::doit() {
ResourceMark rm;
ConcurrentLocksDump concurrent_locks(true);
if (_with_locked_synchronizers) {
concurrent_locks.dump_at_safepoint();
}
if (_num_threads == 0) {
// Snapshot all live threads
for (JavaThread* jt = Threads::first(); jt != NULL; jt = jt->next()) {
if (jt->is_exiting() ||
jt->is_hidden_from_external_view()) {
// skip terminating threads and hidden threads
continue;
}
ThreadConcurrentLocks* tcl = NULL;
if (_with_locked_synchronizers) {
tcl = concurrent_locks.thread_concurrent_locks(jt);
}
ThreadSnapshot* ts = snapshot_thread(jt, tcl);
_result->add_thread_snapshot(ts);
}
} else {
// Snapshot threads in the given _threads array
// A dummy snapshot is created if a thread doesn't exist
for (int i = 0; i < _num_threads; i++) {
instanceHandle th = _threads->at(i);
if (th() == NULL) {
// skip if the thread doesn't exist
// Add a dummy snapshot
_result->add_thread_snapshot(new ThreadSnapshot());
continue;
}
// Dump thread stack only if the thread is alive and not exiting
// and not VM internal thread.
JavaThread* jt = java_lang_Thread::thread(th());
if (jt == NULL || /* thread not alive */
jt->is_exiting() ||
jt->is_hidden_from_external_view()) {
// add a NULL snapshot if skipped
_result->add_thread_snapshot(new ThreadSnapshot());
continue;
}
ThreadConcurrentLocks* tcl = NULL;
if (_with_locked_synchronizers) {
tcl = concurrent_locks.thread_concurrent_locks(jt);
}
ThreadSnapshot* ts = snapshot_thread(jt, tcl);
_result->add_thread_snapshot(ts);
}
}
}
void DirtyCardQueueSet::iterate_closure_all_threads(bool consume,
size_t worker_i) {
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
for(JavaThread* t = Threads::first(); t; t = t->next()) {
bool b = t->dirty_card_queue().apply_closure(_closure, consume);
guarantee(b, "Should not be interrupted.");
}
bool b = shared_dirty_card_queue()->apply_closure(_closure,
consume,
worker_i);
guarantee(b, "Should not be interrupted.");
}
void IdealGraphPrinter::clean_up() {
JavaThread *p;
for (p = Threads::first(); p; p = p->next()) {
if (p->is_Compiler_thread()) {
CompilerThread *c = (CompilerThread *)p;
IdealGraphPrinter *printer = c->ideal_graph_printer();
if (printer) {
delete printer;
}
c->set_ideal_graph_printer(NULL);
}
}
}
int VM_Exit::wait_for_threads_in_native_to_block() {
// VM exits at safepoint. This function must be called at the final safepoint
// to wait for threads in _thread_in_native state to be quiescent.
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint already");
Thread * thr_cur = Thread::current();
Monitor timer(Mutex::leaf, "VM_Exit timer", true,
Monitor::_safepoint_check_never);
// Compiler threads need longer wait because they can access VM data directly
// while in native. If they are active and some structures being used are
// deleted by the shutdown sequence, they will crash. On the other hand, user
// threads must go through native=>Java/VM transitions first to access VM
// data, and they will be stopped during state transition. In theory, we
// don't have to wait for user threads to be quiescent, but it's always
// better to terminate VM when current thread is the only active thread, so
// wait for user threads too. Numbers are in 10 milliseconds.
int max_wait_user_thread = 30; // at least 300 milliseconds
int max_wait_compiler_thread = 1000; // at least 10 seconds
int max_wait = max_wait_compiler_thread;
int attempts = 0;
while (true) {
int num_active = 0;
int num_active_compiler_thread = 0;
for(JavaThread *thr = Threads::first(); thr != NULL; thr = thr->next()) {
if (thr!=thr_cur && thr->thread_state() == _thread_in_native) {
num_active++;
if (thr->is_Compiler_thread()) {
num_active_compiler_thread++;
}
}
}
if (num_active == 0) {
return 0;
} else if (attempts > max_wait) {
return num_active;
} else if (num_active_compiler_thread == 0 && attempts > max_wait_user_thread) {
return num_active;
}
attempts++;
MutexLockerEx ml(&timer, Mutex::_no_safepoint_check_flag);
timer.wait(Mutex::_no_safepoint_check_flag, 10);
}
}
void DirtyCardQueueSet::concatenate_logs() {
// Iterate over all the threads, if we find a partial log add it to
// the global list of logs. Temporarily turn off the limit on the number
// of outstanding buffers.
int save_max_completed_queue = _max_completed_queue;
_max_completed_queue = max_jint;
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
for (JavaThread* t = Threads::first(); t; t = t->next()) {
concatenate_log(t->dirty_card_queue());
}
concatenate_log(_shared_dirty_card_queue);
// Restore the completed buffer queue limit.
_max_completed_queue = save_max_completed_queue;
}
// Check if the NUMA topology has changed. Add and remove spaces if needed.
// The update can be forced by setting the force parameter equal to true.
bool MutableNUMASpace::update_layout(bool force) {
// Check if the topology had changed.
bool changed = os::numa_topology_changed();
if (force || changed) {
// Compute lgrp intersection. Add/remove spaces.
int lgrp_limit = (int)os::numa_get_groups_num();
int *lgrp_ids = NEW_C_HEAP_ARRAY(int, lgrp_limit, mtGC);
int lgrp_num = (int)os::numa_get_leaf_groups(lgrp_ids, lgrp_limit);
assert(lgrp_num > 0, "There should be at least one locality group");
// Add new spaces for the new nodes
for (int i = 0; i < lgrp_num; i++) {
bool found = false;
for (int j = 0; j < lgrp_spaces()->length(); j++) {
if (lgrp_spaces()->at(j)->lgrp_id() == lgrp_ids[i]) {
found = true;
break;
}
}
if (!found) {
lgrp_spaces()->append(new LGRPSpace(lgrp_ids[i], alignment()));
}
}
// Remove spaces for the removed nodes.
for (int i = 0; i < lgrp_spaces()->length();) {
bool found = false;
for (int j = 0; j < lgrp_num; j++) {
if (lgrp_spaces()->at(i)->lgrp_id() == lgrp_ids[j]) {
found = true;
break;
}
}
if (!found) {
delete lgrp_spaces()->at(i);
lgrp_spaces()->remove_at(i);
} else {
i++;
}
}
FREE_C_HEAP_ARRAY(int, lgrp_ids);
if (changed) {
for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
thread->set_lgrp_id(-1);
}
}
return true;
}
void BiasedLocking::preserve_marks() {
if (!UseBiasedLocking)
return;
assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
assert(_preserved_oop_stack == NULL, "double initialization");
assert(_preserved_mark_stack == NULL, "double initialization");
// In order to reduce the number of mark words preserved during GC
// due to the presence of biased locking, we reinitialize most mark
// words to the class's prototype during GC -- even those which have
// a currently valid bias owner. One important situation where we
// must not clobber a bias is when a biased object is currently
// locked. To handle this case we iterate over the currently-locked
// monitors in a prepass and, if they are biased, preserve their
// mark words here. This should be a relatively small set of objects
// especially compared to the number of objects in the heap.
_preserved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(10, true);
_preserved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<Handle>(10, true);
ResourceMark rm;
Thread* cur = Thread::current();
for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
if (thread->has_last_Java_frame()) {
RegisterMap rm(thread);
for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
GrowableArray<MonitorInfo*> *monitors = vf->monitors();
if (monitors != NULL) {
int len = monitors->length();
// Walk monitors youngest to oldest
for (int i = len - 1; i >= 0; i--) {
MonitorInfo* mon_info = monitors->at(i);
if (mon_info->owner_is_scalar_replaced()) continue;
oop owner = mon_info->owner();
if (owner != NULL) {
markOop mark = owner->mark();
if (mark->has_bias_pattern()) {
_preserved_oop_stack->push(Handle(cur, owner));
_preserved_mark_stack->push(mark);
}
}
}
}
}
}
}
}
void ThreadLocalAllocBuffer::accumulate_statistics_before_gc() {
global_stats()->initialize();
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
thread->tlab().accumulate_statistics();
thread->tlab().initialize_statistics();
}
// Publish new stats if some allocation occurred.
if (global_stats()->allocation() != 0) {
global_stats()->publish();
if (PrintTLAB) {
global_stats()->print();
}
}
}
int VM_Exit::set_vm_exited() {
Thread * thr_cur = ThreadLocalStorage::get_thread_slow();
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint already");
int num_active = 0;
_shutdown_thread = thr_cur;
_vm_exited = true; // global flag
for(JavaThread *thr = Threads::first(); thr != NULL; thr = thr->next())
if (thr!=thr_cur && thr->thread_state() == _thread_in_native) {
++num_active;
thr->set_terminated(JavaThread::_vm_exited); // per-thread flag
}
return num_active;
}
void FlatProfiler::record_thread_ticks() {
int maxthreads, suspendedthreadcount;
JavaThread** threadsList;
bool interval_expired = false;
if (ProfileIntervals &&
(FlatProfiler::received_ticks >= interval_ticks_previous + ProfileIntervalsTicks)) {
interval_expired = true;
interval_ticks_previous = FlatProfiler::received_ticks;
}
// Try not to wait for the Threads_lock
if (Threads_lock->try_lock()) {
{ // Threads_lock scope
maxthreads = Threads::number_of_threads();
threadsList = NEW_C_HEAP_ARRAY(JavaThread *, maxthreads, mtInternal);
suspendedthreadcount = 0;
for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) {
if (tp->is_Compiler_thread()) {
// Only record ticks for active compiler threads
CompilerThread* cthread = (CompilerThread*)tp;
if (cthread->task() != NULL) {
// The compiler is active. If we need to access any of the fields
// of the compiler task we should suspend the CompilerThread first.
FlatProfiler::compiler_ticks += 1;
continue;
}
}
// First externally suspend all threads by marking each for
// external suspension - so it will stop at its next transition
// Then do a safepoint
ThreadProfiler* pp = tp->get_thread_profiler();
if (pp != NULL && pp->engaged) {
MutexLockerEx ml(tp->SR_lock(), Mutex::_no_safepoint_check_flag);
if (!tp->is_external_suspend() && !tp->is_exiting()) {
tp->set_external_suspend();
threadsList[suspendedthreadcount++] = tp;
}
}
}
Threads_lock->unlock();
}
int VM_Exit::set_vm_exited() {
CodeCacheExtensions::complete_step(CodeCacheExtensionsSteps::LastStep);
Thread * thr_cur = Thread::current();
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint already");
int num_active = 0;
_shutdown_thread = thr_cur;
_vm_exited = true; // global flag
for(JavaThread *thr = Threads::first(); thr != NULL; thr = thr->next())
if (thr!=thr_cur && thr->thread_state() == _thread_in_native) {
++num_active;
thr->set_terminated(JavaThread::_vm_exited); // per-thread flag
}
return num_active;
}
void print_statistics() {
if (CITime) {
CompileBroker::_c1.print_times();
CompileBroker::_c2.print_times();
}
if( ProfileMMU ) {
MutexLockerAllowGC mu(Threads_lock, JavaThread::current());
for( JavaThread* X = Threads::first(); X; X = X->next() )
if( X->mmu() ) X->mmu()->fold_into_global();
MMU::print(NULL);
}
if (PrintLockContentionAtExit) {
MutexLocker::print_lock_contention(NULL);
AzLock::print_lock_hold_times(NULL);
}
}
ThreadsListEnumerator::ThreadsListEnumerator(Thread* cur_thread,
bool include_jvmti_agent_threads,
bool include_jni_attaching_threads) {
assert(cur_thread == Thread::current(), "Check current thread");
int init_size = ThreadService::get_live_thread_count();
_threads_array = new GrowableArray<instanceHandle>(init_size);
MutexLockerEx ml(Threads_lock);
for (JavaThread* jt = Threads::first(); jt != NULL; jt = jt->next()) {
// skips JavaThreads in the process of exiting
// and also skips VM internal JavaThreads
// Threads in _thread_new or _thread_new_trans state are included.
// i.e. threads have been started but not yet running.
if (jt->threadObj() == NULL ||
jt->is_exiting() ||
!java_lang_Thread::is_alive(jt->threadObj()) ||
jt->is_hidden_from_external_view()) {
continue;
}
// skip agent threads
if (!include_jvmti_agent_threads && jt->is_jvmti_agent_thread()) {
continue;
}
// skip jni threads in the process of attaching
if (!include_jni_attaching_threads && jt->is_attaching_via_jni()) {
continue;
}
instanceHandle h(cur_thread, (instanceOop) jt->threadObj());
_threads_array->append(h);
}
}
void print_statistics() {
#ifdef ASSERT
if (CountJNICalls) {
extern Histogram *JNIHistogram;
JNIHistogram->print(tty);
}
if (CountJVMCalls) {
extern Histogram *JVMHistogram;
JVMHistogram->print(tty);
}
#endif
Statistics::stats_print();
if (MemProfiling) {
MemProfiler::disengage();
}
if (CITime) {
CompileBroker::_c1.print_times();
CompileBroker::_c2.print_times();
}
if( PrintStatistics ) {
SharedRuntime::print_statistics();
CompiledIC::print_statistics();
Deoptimization::print_statistics();
if (UseC1) Runtime1::print_statistics();
if (UseC2) {
Parse::print_statistics();
PhaseCCP::print_statistics();
PhaseRegAlloc::print_statistics();
PhasePeephole::print_statistics();
PhaseIdealLoop::print_statistics();
if (TimeLivenessAnalysis) MethodLiveness::print_times();
if (TimeCompiler) Compile::print_timers();
}
os::print_statistics();
if(TimeCompilationPolicy)CompilationPolicy::print_time();
#ifndef PRODUCT
if (LogCompilerOutput) {
if (UseC1) tty->print_cr("C1 Log Output Size: %ld", Compilation::_c1outputsize);
if (UseC2) tty->print_cr("C2 Log Output Size: %ld", Compile::_c2outputsize);
}
#endif
}
if (ProfilerCheckIntervals) {
PeriodicTask::print_intervals();
}
if( ProfileMMU ) {
{
MutexLockerAllowGC mu(Threads_lock, JavaThread::current());
for( JavaThread* X = Threads::first(); X; X = X->next() )
if( X->mmu() ) X->mmu()->fold_into_global();
}
MMU::print(NULL);
}
if (PrintSymbolTableSizeHistogram) {
SymbolTable::print_histogram();
}
if (CountBytecodes || TraceBytecodes || StopInterpreterAt) {
BytecodeCounter::print();
}
if (PrintCodeCache) {
assert0(Thread::current()->is_Java_thread() && ((JavaThread*)Thread::current())->jvm_locked_by_self());
CodeCache::print();
CodeCache::print_internals();
}
if (PrintLockContentionAtExit) {
MutexLocker::print_lock_contention(NULL);
AzLock::print_lock_hold_times(NULL);
}
if (PrintClassStatistics) {
SystemDictionary::print_class_statistics();
}
if (PrintMethodStatistics) {
SystemDictionary::print_method_statistics();
}
print_bytecode_count();
if (PrintSystemDictionaryAtExit) {
SystemDictionary::print();
}
//---------------------------------
/* Turn on for memcpy profiling.
See matching code in //azul/main-dev/gnu/newlib-1.11.0/newlib/libc/machine/azul/memcpy.S
printf("memcpy Size histogram\n");
jlong total_bytes = 0;
for( int i=0; i<128; i++ )
total_bytes += (jlong)i*(jlong)memcpy_size_histogram[i];
for( int i=7; i<32; i++ )
total_bytes += (1LL<<i)*(jlong)memcpy_size_histogram[128+i-7];
jlong invokes = 0;
for( int i=0; i<sizeof(memcpy_size_histogram)/sizeof(memcpy_size_histogram[0]); i++ )
invokes += memcpy_size_histogram[i];
printf("bytes cnt\n");
for( int i=0; i<128; i++ )
print_memcpy_size_histo(i,memcpy_size_histogram[i],total_bytes, invokes);
for( int i=7; i<32; i++ )
print_memcpy_size_histo(1L<<i,memcpy_size_histogram[128+(i-7)],total_bytes, invokes);
printf("\n");
fflush(stdout);
printf("memcpy Alignment histogram\n");
printf("alignment dst src|dst src^dst src|dst|len\n");
jlong cum_dst=invokes, cum_src_dst=invokes, cum_src_xor=invokes, cum_src_len=invokes;
for( int i=0; i<32; i++ ) {
if( dst_align[i] ||
src_or_dst_align[i] ||
src_xor_dst_align[i] ||
src_or_dst_or_len_align[i] ) {
printf("%8d",1L<<i);
cum_dst = print_align( dst_align[i], cum_dst , invokes );
cum_src_dst = print_align( src_or_dst_align[i], cum_src_dst, invokes );
cum_src_xor = print_align( src_xor_dst_align[i], cum_src_xor, invokes );
cum_src_len = print_align( src_or_dst_or_len_align[i], cum_src_len, invokes );
printf("\n");
}
}
printf("total word-misaligned bytes moved: %lld (%5.2f%%)",
memcpy_misalign_bytes, (double)memcpy_misalign_bytes/(double)total_bytes);
printf("\n");
*/
fflush(stdout);
}
// Find deadlocks involving object monitors and concurrent locks if concurrent_locks is true
DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(bool concurrent_locks) {
// This code was modified from the original Threads::find_deadlocks code.
int globalDfn = 0, thisDfn;
ObjectMonitor* waitingToLockMonitor = NULL;
oop waitingToLockBlocker = NULL;
bool blocked_on_monitor = false;
JavaThread *currentThread, *previousThread;
int num_deadlocks = 0;
for (JavaThread* p = Threads::first(); p != NULL; p = p->next()) {
// Initialize the depth-first-number
p->set_depth_first_number(-1);
}
DeadlockCycle* deadlocks = NULL;
DeadlockCycle* last = NULL;
DeadlockCycle* cycle = new DeadlockCycle();
for (JavaThread* jt = Threads::first(); jt != NULL; jt = jt->next()) {
if (jt->depth_first_number() >= 0) {
// this thread was already visited
continue;
}
thisDfn = globalDfn;
jt->set_depth_first_number(globalDfn++);
previousThread = jt;
currentThread = jt;
cycle->reset();
// When there is a deadlock, all the monitors involved in the dependency
// cycle must be contended and heavyweight. So we only care about the
// heavyweight monitor a thread is waiting to lock.
waitingToLockMonitor = (ObjectMonitor*)jt->current_pending_monitor();
if (concurrent_locks) {
waitingToLockBlocker = jt->current_park_blocker();
}
while (waitingToLockMonitor != NULL || waitingToLockBlocker != NULL) {
cycle->add_thread(currentThread);
if (waitingToLockMonitor != NULL) {
address currentOwner = (address)waitingToLockMonitor->owner();
if (currentOwner != NULL) {
currentThread = Threads::owning_thread_from_monitor_owner(
currentOwner,
false /* no locking needed */);
if (currentThread == NULL) {
// This function is called at a safepoint so the JavaThread
// that owns waitingToLockMonitor should be findable, but
// if it is not findable, then the previous currentThread is
// blocked permanently. We record this as a deadlock.
num_deadlocks++;
cycle->set_deadlock(true);
// add this cycle to the deadlocks list
if (deadlocks == NULL) {
deadlocks = cycle;
} else {
last->set_next(cycle);
}
last = cycle;
cycle = new DeadlockCycle();
break;
}
}
} else {
if (concurrent_locks) {
if (waitingToLockBlocker->is_a(SystemDictionary::abstract_ownable_synchronizer_klass())) {
oop threadObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
currentThread = threadObj != NULL ? java_lang_Thread::thread(threadObj) : NULL;
} else {
currentThread = NULL;
}
}
}
if (currentThread == NULL) {
// No dependency on another thread
break;
}
if (currentThread->depth_first_number() < 0) {
// First visit to this thread
currentThread->set_depth_first_number(globalDfn++);
} else if (currentThread->depth_first_number() < thisDfn) {
// Thread already visited, and not on a (new) cycle
break;
} else if (currentThread == previousThread) {
// Self-loop, ignore
break;
} else {
// We have a (new) cycle
num_deadlocks++;
cycle->set_deadlock(true);
// add this cycle to the deadlocks list
if (deadlocks == NULL) {
deadlocks = cycle;
} else {
last->set_next(cycle);
}
last = cycle;
cycle = new DeadlockCycle();
break;
}
previousThread = currentThread;
waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();
if (concurrent_locks) {
waitingToLockBlocker = currentThread->current_park_blocker();
}
}
}
delete cycle;
return deadlocks;
}
static void find(intptr_t x, bool print_pc) {
address addr = (address)x;
CodeBlob* b = CodeCache::find_blob_unsafe(addr);
if (b != NULL) {
if (b->is_buffer_blob()) {
// the interpreter is generated into a buffer blob
InterpreterCodelet* i = Interpreter::codelet_containing(addr);
if (i != NULL) {
i->print();
return;
}
if (Interpreter::contains(addr)) {
tty->print_cr(INTPTR_FORMAT " is pointing into interpreter code (not bytecode specific)", addr);
return;
}
//
if (AdapterHandlerLibrary::contains(b)) {
AdapterHandlerLibrary::print_handler(b);
}
// the stubroutines are generated into a buffer blob
StubCodeDesc* d = StubCodeDesc::desc_for(addr);
if (d != NULL) {
d->print();
if (print_pc) tty->cr();
return;
}
if (StubRoutines::contains(addr)) {
tty->print_cr(INTPTR_FORMAT " is pointing to an (unnamed) stub routine", addr);
return;
}
// the InlineCacheBuffer is using stubs generated into a buffer blob
if (InlineCacheBuffer::contains(addr)) {
tty->print_cr(INTPTR_FORMAT " is pointing into InlineCacheBuffer", addr);
return;
}
VtableStub* v = VtableStubs::stub_containing(addr);
if (v != NULL) {
v->print();
return;
}
}
if (print_pc && b->is_nmethod()) {
ResourceMark rm;
tty->print("%#p: Compiled ", addr);
((nmethod*)b)->method()->print_value_on(tty);
tty->print(" = (CodeBlob*)" INTPTR_FORMAT, b);
tty->cr();
return;
}
if ( b->is_nmethod()) {
if (b->is_zombie()) {
tty->print_cr(INTPTR_FORMAT " is zombie nmethod", b);
} else if (b->is_not_entrant()) {
tty->print_cr(INTPTR_FORMAT " is non-entrant nmethod", b);
}
}
b->print();
return;
}
if (Universe::heap()->is_in(addr)) {
HeapWord* p = Universe::heap()->block_start(addr);
bool print = false;
// If we couldn't find it it just may mean that heap wasn't parseable
// See if we were just given an oop directly
if (p != NULL && Universe::heap()->block_is_obj(p)) {
print = true;
} else if (p == NULL && ((oopDesc*)addr)->is_oop()) {
p = (HeapWord*) addr;
print = true;
}
if (print) {
oop(p)->print();
if (p != (HeapWord*)x && oop(p)->is_constMethod() &&
constMethodOop(p)->contains(addr)) {
Thread *thread = Thread::current();
HandleMark hm(thread);
methodHandle mh (thread, constMethodOop(p)->method());
if (!mh->is_native()) {
tty->print_cr("bci_from(%p) = %d; print_codes():",
addr, mh->bci_from(address(x)));
mh->print_codes();
}
}
return;
}
} else if (Universe::heap()->is_in_reserved(addr)) {
tty->print_cr(INTPTR_FORMAT " is an unallocated location in the heap", addr);
return;
}
if (JNIHandles::is_global_handle((jobject) addr)) {
tty->print_cr(INTPTR_FORMAT " is a global jni handle", addr);
return;
}
if (JNIHandles::is_weak_global_handle((jobject) addr)) {
tty->print_cr(INTPTR_FORMAT " is a weak global jni handle", addr);
return;
}
if (JNIHandleBlock::any_contains((jobject) addr)) {
tty->print_cr(INTPTR_FORMAT " is a local jni handle", addr);
return;
}
for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
// Check for privilege stack
if (thread->privileged_stack_top() != NULL && thread->privileged_stack_top()->contains(addr)) {
tty->print_cr(INTPTR_FORMAT " is pointing into the privilege stack for thread: " INTPTR_FORMAT, addr, thread);
return;
}
// If the addr is a java thread print information about that.
if (addr == (address)thread) {
thread->print();
return;
}
}
// Try an OS specific find
if (os::find(addr)) {
return;
}
if (print_pc) {
tty->print_cr(INTPTR_FORMAT ": probably in C++ code; check debugger", addr);
Disassembler::decode(same_page(addr-40,addr),same_page(addr+40,addr));
return;
}
tty->print_cr(INTPTR_FORMAT " is pointing to unknown location", addr);
}
// Compute truly enabled events - meaning if the event can and could be
// sent. An event is truly enabled if it is user enabled on the thread
// or globally user enabled, but only if there is a callback or event hook
// for it and, for field watch and frame pop, one has been set.
// Compute if truly enabled, per thread, per environment, per combination
// (thread x environment), and overall. These merges are true if any is true.
// True per thread if some environment has callback set and the event is globally
// enabled or enabled for this thread.
// True per environment if the callback is set and the event is globally
// enabled in this environment or enabled for any thread in this environment.
// True per combination if the environment has the callback set and the
// event is globally enabled in this environment or the event is enabled
// for this thread and environment.
//
// All states transitions dependent on these transitions are also handled here.
void
JvmtiEventControllerPrivate::recompute_enabled() {
assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
// event enabled for any thread in any environment
jlong was_any_env_thread_enabled = JvmtiEventController::_universal_global_event_enabled.get_bits();
jlong any_env_thread_enabled = 0;
EC_TRACE(("JVMTI [-] # recompute enabled - before " UINT64_FORMAT_X, was_any_env_thread_enabled));
// compute non-thread-filters events.
// This must be done separately from thread-filtered events, since some
// events can occur before any threads exist.
JvmtiEnvIterator it;
for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
any_env_thread_enabled |= recompute_env_enabled(env);
}
// We need to create any missing jvmti_thread_state if there are globally set thread
// filtered events and there weren't last time
if ( (any_env_thread_enabled & THREAD_FILTERED_EVENT_BITS) != 0 &&
(was_any_env_thread_enabled & THREAD_FILTERED_EVENT_BITS) == 0) {
assert(JvmtiEnv::is_vm_live() || (JvmtiEnv::get_phase()==JVMTI_PHASE_START),
"thread filtered events should not be enabled when VM not in start or live phase");
{
MutexLocker mu(Threads_lock); //hold the Threads_lock for the iteration
for (JavaThread *tp = Threads::first(); tp != NULL; tp = tp->next()) {
// state_for_while_locked() makes tp->is_exiting() check
JvmtiThreadState::state_for_while_locked(tp); // create the thread state if missing
}
}// release Threads_lock
}
// compute and set thread-filtered events
for (JvmtiThreadState *state = JvmtiThreadState::first(); state != NULL; state = state->next()) {
any_env_thread_enabled |= recompute_thread_enabled(state);
}
// set universal state (across all envs and threads)
jlong delta = any_env_thread_enabled ^ was_any_env_thread_enabled;
if (delta != 0) {
JvmtiExport::set_should_post_field_access((any_env_thread_enabled & FIELD_ACCESS_BIT) != 0);
JvmtiExport::set_should_post_field_modification((any_env_thread_enabled & FIELD_MODIFICATION_BIT) != 0);
JvmtiExport::set_should_post_class_load((any_env_thread_enabled & CLASS_LOAD_BIT) != 0);
JvmtiExport::set_should_post_class_file_load_hook((any_env_thread_enabled & CLASS_FILE_LOAD_HOOK_BIT) != 0);
JvmtiExport::set_should_post_native_method_bind((any_env_thread_enabled & NATIVE_METHOD_BIND_BIT) != 0);
JvmtiExport::set_should_post_dynamic_code_generated((any_env_thread_enabled & DYNAMIC_CODE_GENERATED_BIT) != 0);
JvmtiExport::set_should_post_data_dump((any_env_thread_enabled & DATA_DUMP_BIT) != 0);
JvmtiExport::set_should_post_class_prepare((any_env_thread_enabled & CLASS_PREPARE_BIT) != 0);
JvmtiExport::set_should_post_class_unload((any_env_thread_enabled & CLASS_UNLOAD_BIT) != 0);
JvmtiExport::set_should_post_monitor_contended_enter((any_env_thread_enabled & MONITOR_CONTENDED_ENTER_BIT) != 0);
JvmtiExport::set_should_post_monitor_contended_entered((any_env_thread_enabled & MONITOR_CONTENDED_ENTERED_BIT) != 0);
JvmtiExport::set_should_post_monitor_wait((any_env_thread_enabled & MONITOR_WAIT_BIT) != 0);
JvmtiExport::set_should_post_monitor_waited((any_env_thread_enabled & MONITOR_WAITED_BIT) != 0);
JvmtiExport::set_should_post_garbage_collection_start((any_env_thread_enabled & GARBAGE_COLLECTION_START_BIT) != 0);
JvmtiExport::set_should_post_garbage_collection_finish((any_env_thread_enabled & GARBAGE_COLLECTION_FINISH_BIT) != 0);
JvmtiExport::set_should_post_object_free((any_env_thread_enabled & OBJECT_FREE_BIT) != 0);
JvmtiExport::set_should_post_resource_exhausted((any_env_thread_enabled & RESOURCE_EXHAUSTED_BIT) != 0);
JvmtiExport::set_should_post_compiled_method_load((any_env_thread_enabled & COMPILED_METHOD_LOAD_BIT) != 0);
JvmtiExport::set_should_post_compiled_method_unload((any_env_thread_enabled & COMPILED_METHOD_UNLOAD_BIT) != 0);
JvmtiExport::set_should_post_vm_object_alloc((any_env_thread_enabled & VM_OBJECT_ALLOC_BIT) != 0);
// need this if we want thread events or we need them to init data
JvmtiExport::set_should_post_thread_life((any_env_thread_enabled & NEED_THREAD_LIFE_EVENTS) != 0);
// If single stepping is turned on or off, execute the VM op to change it.
if (delta & SINGLE_STEP_BIT) {
switch (JvmtiEnv::get_phase()) {
case JVMTI_PHASE_DEAD:
// If the VM is dying we can't execute VM ops
break;
case JVMTI_PHASE_LIVE: {
VM_ChangeSingleStep op((any_env_thread_enabled & SINGLE_STEP_BIT) != 0);
VMThread::execute(&op);
break;
}
default:
assert(false, "should never come here before live phase");
break;
}
}
// set global truly enabled, that is, any thread in any environment
JvmtiEventController::_universal_global_event_enabled.set_bits(any_env_thread_enabled);
// set global should_post_on_exceptions
JvmtiExport::set_should_post_on_exceptions((any_env_thread_enabled & SHOULD_POST_ON_EXCEPTIONS_BITS) != 0);
}
EC_TRACE(("JVMTI [-] # recompute enabled - after " UINT64_FORMAT_X, any_env_thread_enabled));
}
static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o,
bool bulk_rebias,
bool attempt_rebias_of_object,
JavaThread* requesting_thread) {
assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
if (TraceBiasedLocking) {
tty->print_cr("* Beginning bulk revocation (kind == %s) because of object "
INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
(bulk_rebias ? "rebias" : "revoke"),
p2i((void *) o), (intptr_t) o->mark(), o->klass()->external_name());
}
jlong cur_time = os::javaTimeMillis();
o->klass()->set_last_biased_lock_bulk_revocation_time(cur_time);
Klass* k_o = o->klass();
Klass* klass = k_o;
if (bulk_rebias) {
// Use the epoch in the klass of the object to implicitly revoke
// all biases of objects of this data type and force them to be
// reacquired. However, we also need to walk the stacks of all
// threads and update the headers of lightweight locked objects
// with biases to have the current epoch.
// If the prototype header doesn't have the bias pattern, don't
// try to update the epoch -- assume another VM operation came in
// and reset the header to the unbiased state, which will
// implicitly cause all existing biases to be revoked
if (klass->prototype_header()->has_bias_pattern()) {
int prev_epoch = klass->prototype_header()->bias_epoch();
klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch());
int cur_epoch = klass->prototype_header()->bias_epoch();
// Now walk all threads' stacks and adjust epochs of any biased
// and locked objects of this data type we encounter
for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
for (int i = 0; i < cached_monitor_info->length(); i++) {
MonitorInfo* mon_info = cached_monitor_info->at(i);
oop owner = mon_info->owner();
markOop mark = owner->mark();
if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
// We might have encountered this object already in the case of recursive locking
assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment");
owner->set_mark(mark->set_bias_epoch(cur_epoch));
}
}
}
}
// At this point we're done. All we have to do is potentially
// adjust the header of the given object to revoke its bias.
revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread);
} else {
if (TraceBiasedLocking) {
ResourceMark rm;
tty->print_cr("* Disabling biased locking for type %s", klass->external_name());
}
// Disable biased locking for this data type. Not only will this
// cause future instances to not be biased, but existing biased
// instances will notice that this implicitly caused their biases
// to be revoked.
klass->set_prototype_header(markOopDesc::prototype());
// Now walk all threads' stacks and forcibly revoke the biases of
// any locked and biased objects of this data type we encounter.
for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
for (int i = 0; i < cached_monitor_info->length(); i++) {
MonitorInfo* mon_info = cached_monitor_info->at(i);
oop owner = mon_info->owner();
markOop mark = owner->mark();
if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
revoke_bias(owner, false, true, requesting_thread);
}
}
}
// Must force the bias of the passed object to be forcibly revoked
// as well to ensure guarantees to callers
revoke_bias(o, false, true, requesting_thread);
}
if (TraceBiasedLocking) {
tty->print_cr("* Ending bulk revocation");
}
BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED;
if (attempt_rebias_of_object &&
o->mark()->has_bias_pattern() &&
klass->prototype_header()->has_bias_pattern()) {
markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(),
klass->prototype_header()->bias_epoch());
o->set_mark(new_mark);
status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED;
if (TraceBiasedLocking) {
tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread);
}
}
assert(!o->mark()->has_bias_pattern() ||
(attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)),
"bug in bulk bias revocation");
return status_code;
}
static void clean_up_cached_monitor_info() {
// Walk the thread list clearing out the cached monitors
for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
thr->set_cached_monitor_info(NULL);
}
}
// Roll all threads forward to a safepoint and suspend them all
void SafepointSynchronize::begin() {
Thread* myThread = Thread::current();
assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
_safepoint_begin_time = os::javaTimeNanos();
_ts_of_current_safepoint = tty->time_stamp().seconds();
}
#if INCLUDE_ALL_GCS
if (UseConcMarkSweepGC) {
// In the future we should investigate whether CMS can use the
// more-general mechanism below. DLD (01/05).
ConcurrentMarkSweepThread::synchronize(false);
} else if (UseG1GC) {
SuspendibleThreadSet::synchronize();
}
#endif // INCLUDE_ALL_GCS
// By getting the Threads_lock, we assure that no threads are about to start or
// exit. It is released again in SafepointSynchronize::end().
Threads_lock->lock();
assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
int nof_threads = Threads::number_of_threads();
if (TraceSafepoint) {
tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
}
RuntimeService::record_safepoint_begin();
MutexLocker mu(Safepoint_lock);
// Reset the count of active JNI critical threads
_current_jni_active_count = 0;
// Set number of threads to wait for, before we initiate the callbacks
_waiting_to_block = nof_threads;
TryingToBlock = 0 ;
int still_running = nof_threads;
// Save the starting time, so that it can be compared to see if this has taken
// too long to complete.
jlong safepoint_limit_time;
timeout_error_printed = false;
// PrintSafepointStatisticsTimeout can be specified separately. When
// specified, PrintSafepointStatistics will be set to true in
// deferred_initialize_stat method. The initialization has to be done
// early enough to avoid any races. See bug 6880029 for details.
if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
deferred_initialize_stat();
}
// Begin the process of bringing the system to a safepoint.
// Java threads can be in several different states and are
// stopped by different mechanisms:
//
// 1. Running interpreted
// The interpeter dispatch table is changed to force it to
// check for a safepoint condition between bytecodes.
// 2. Running in native code
// When returning from the native code, a Java thread must check
// the safepoint _state to see if we must block. If the
// VM thread sees a Java thread in native, it does
// not wait for this thread to block. The order of the memory
// writes and reads of both the safepoint state and the Java
// threads state is critical. In order to guarantee that the
// memory writes are serialized with respect to each other,
// the VM thread issues a memory barrier instruction
// (on MP systems). In order to avoid the overhead of issuing
// a memory barrier for each Java thread making native calls, each Java
// thread performs a write to a single memory page after changing
// the thread state. The VM thread performs a sequence of
// mprotect OS calls which forces all previous writes from all
// Java threads to be serialized. This is done in the
// os::serialize_thread_states() call. This has proven to be
// much more efficient than executing a membar instruction
// on every call to native code.
// 3. Running compiled Code
// Compiled code reads a global (Safepoint Polling) page that
// is set to fault if we are trying to get to a safepoint.
// 4. Blocked
// A thread which is blocked will not be allowed to return from the
// block condition until the safepoint operation is complete.
// 5. In VM or Transitioning between states
// If a Java thread is currently running in the VM or transitioning
// between states, the safepointing code will wait for the thread to
// block itself when it attempts transitions to a new state.
//
_state = _synchronizing;
OrderAccess::fence();
// Flush all thread states to memory
if (!UseMembar) {
os::serialize_thread_states();
}
// Make interpreter safepoint aware
Interpreter::notice_safepoints();
if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
// Make polling safepoint aware
guarantee (PageArmed == 0, "invariant") ;
PageArmed = 1 ;
os::make_polling_page_unreadable();
}
// Consider using active_processor_count() ... but that call is expensive.
int ncpus = os::processor_count() ;
#ifdef ASSERT
for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
assert(cur->safepoint_state()->is_running(), "Illegal initial state");
// Clear the visited flag to ensure that the critical counts are collected properly.
cur->set_visited_for_critical_count(false);
}
#endif // ASSERT
if (SafepointTimeout)
safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
// Iterate through all threads until it have been determined how to stop them all at a safepoint
unsigned int iterations = 0;
int steps = 0 ;
while(still_running > 0) {
for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
ThreadSafepointState *cur_state = cur->safepoint_state();
if (cur_state->is_running()) {
cur_state->examine_state_of_thread();
if (!cur_state->is_running()) {
still_running--;
// consider adjusting steps downward:
// steps = 0
// steps -= NNN
// steps >>= 1
// steps = MIN(steps, 2000-100)
// if (iterations != 0) steps -= NNN
}
if (TraceSafepoint && Verbose) cur_state->print();
}
}
if (PrintSafepointStatistics && iterations == 0) {
begin_statistics(nof_threads, still_running);
}
if (still_running > 0) {
// Check for if it takes to long
if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
print_safepoint_timeout(_spinning_timeout);
}
// Spin to avoid context switching.
// There's a tension between allowing the mutators to run (and rendezvous)
// vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
// a mutator might otherwise use profitably to reach a safepoint. Excessive
// spinning by the VM thread on a saturated system can increase rendezvous latency.
// Blocking or yielding incur their own penalties in the form of context switching
// and the resultant loss of $ residency.
//
// Further complicating matters is that yield() does not work as naively expected
// on many platforms -- yield() does not guarantee that any other ready threads
// will run. As such we revert yield_all() after some number of iterations.
// Yield_all() is implemented as a short unconditional sleep on some platforms.
// Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
// can actually increase the time it takes the VM thread to detect that a system-wide
// stop-the-world safepoint has been reached. In a pathological scenario such as that
// described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
// In that case the mutators will be stalled waiting for the safepoint to complete and the
// the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
// will eventually wake up and detect that all mutators are safe, at which point
// we'll again make progress.
//
// Beware too that that the VMThread typically runs at elevated priority.
// Its default priority is higher than the default mutator priority.
// Obviously, this complicates spinning.
//
// Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
// Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
//
// See the comments in synchronizer.cpp for additional remarks on spinning.
//
// In the future we might:
// 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
// This is tricky as the path used by a thread exiting the JVM (say on
// on JNI call-out) simply stores into its state field. The burden
// is placed on the VM thread, which must poll (spin).
// 2. Find something useful to do while spinning. If the safepoint is GC-related
// we might aggressively scan the stacks of threads that are already safe.
// 3. Use Solaris schedctl to examine the state of the still-running mutators.
// If all the mutators are ONPROC there's no reason to sleep or yield.
// 4. YieldTo() any still-running mutators that are ready but OFFPROC.
// 5. Check system saturation. If the system is not fully saturated then
// simply spin and avoid sleep/yield.
// 6. As still-running mutators rendezvous they could unpark the sleeping
// VMthread. This works well for still-running mutators that become
// safe. The VMthread must still poll for mutators that call-out.
// 7. Drive the policy on time-since-begin instead of iterations.
// 8. Consider making the spin duration a function of the # of CPUs:
// Spin = (((ncpus-1) * M) + K) + F(still_running)
// Alternately, instead of counting iterations of the outer loop
// we could count the # of threads visited in the inner loop, above.
// 9. On windows consider using the return value from SwitchThreadTo()
// to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
guarantee (PageArmed == 0, "invariant") ;
PageArmed = 1 ;
os::make_polling_page_unreadable();
}
// Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
// ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
++steps ;
if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
SpinPause() ; // MP-Polite spin
} else
if (steps < DeferThrSuspendLoopCount) {
os::NakedYield() ;
} else {
os::yield_all(steps) ;
// Alternately, the VM thread could transiently depress its scheduling priority or
// transiently increase the priority of the tardy mutator(s).
}
iterations ++ ;
}
assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
}
assert(still_running == 0, "sanity check");
if (PrintSafepointStatistics) {
update_statistics_on_spin_end();
}
// wait until all threads are stopped
while (_waiting_to_block > 0) {
if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
if (!SafepointTimeout || timeout_error_printed) {
Safepoint_lock->wait(true); // true, means with no safepoint checks
} else {
// Compute remaining time
jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
// If there is no remaining time, then there is an error
if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
print_safepoint_timeout(_blocking_timeout);
}
}
}
assert(_waiting_to_block == 0, "sanity check");
#ifndef PRODUCT
if (SafepointTimeout) {
jlong current_time = os::javaTimeNanos();
if (safepoint_limit_time < current_time) {
tty->print_cr("# SafepointSynchronize: Finished after "
INT64_FORMAT_W(6) " ms",
((current_time - safepoint_limit_time) / MICROUNITS +
SafepointTimeoutDelay));
}
}
#endif
assert((_safepoint_counter & 0x1) == 0, "must be even");
assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
_safepoint_counter ++;
// Record state
_state = _synchronized;
OrderAccess::fence();
#ifdef ASSERT
for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
// make sure all the threads were visited
assert(cur->was_visited_for_critical_count(), "missed a thread");
}
#endif // ASSERT
// Update the count of active JNI critical regions
GC_locker::set_jni_lock_count(_current_jni_active_count);
if (TraceSafepoint) {
VM_Operation *op = VMThread::vm_operation();
tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
}
RuntimeService::record_safepoint_synchronized();
if (PrintSafepointStatistics) {
update_statistics_on_sync_end(os::javaTimeNanos());
}
// Call stuff that needs to be run when a safepoint is just about to be completed
do_cleanup_tasks();
if (PrintSafepointStatistics) {
// Record how much time spend on the above cleanup tasks
update_statistics_on_cleanup_end(os::javaTimeNanos());
}
}
