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8278389: SuspendibleThreadSet::_suspend_all should be volatile/atomic

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Reviewed-by: ayang, mli
This commit is contained in:
Thomas Schatzl 2021-12-16 12:29:57 +00:00
parent e82310f360
commit aec1b039b3
2 changed files with 19 additions and 15 deletions
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20
src/hotspot/share/gc/shared/suspendibleThreadSet.cpp
View file

@ -31,7 +31,7 @@
uint SuspendibleThreadSet::_nthreads = 0; uint SuspendibleThreadSet::_nthreads = 0;
uint SuspendibleThreadSet::_nthreads_stopped = 0; uint SuspendibleThreadSet::_nthreads_stopped = 0;
bool SuspendibleThreadSet::_suspend_all = false; volatile bool SuspendibleThreadSet::_suspend_all = false;
double SuspendibleThreadSet::_suspend_all_start = 0.0; double SuspendibleThreadSet::_suspend_all_start = 0.0;
static Semaphore* _synchronize_wakeup = NULL; static Semaphore* _synchronize_wakeup = NULL;
@ -50,7 +50,7 @@ bool SuspendibleThreadSet::is_synchronized() {
void SuspendibleThreadSet::join() { void SuspendibleThreadSet::join() {
assert(!Thread::current()->is_suspendible_thread(), "Thread already joined"); assert(!Thread::current()->is_suspendible_thread(), "Thread already joined");
MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag); MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag);
while (_suspend_all) { while (suspend_all()) {
ml.wait(); ml.wait();
} }
_nthreads++; _nthreads++;
@ -63,7 +63,7 @@ void SuspendibleThreadSet::leave() {
assert(_nthreads > 0, "Invalid"); assert(_nthreads > 0, "Invalid");
DEBUG_ONLY(Thread::current()->clear_suspendible_thread();) DEBUG_ONLY(Thread::current()->clear_suspendible_thread();)
_nthreads--; _nthreads--;
if (_suspend_all && is_synchronized()) { if (suspend_all() && is_synchronized()) {
// This leave completes a request, so inform the requestor. // This leave completes a request, so inform the requestor.
_synchronize_wakeup->signal(); _synchronize_wakeup->signal();
} }
@ -72,7 +72,7 @@ void SuspendibleThreadSet::leave() {
void SuspendibleThreadSet::yield() { void SuspendibleThreadSet::yield() {
assert(Thread::current()->is_suspendible_thread(), "Must have joined"); assert(Thread::current()->is_suspendible_thread(), "Must have joined");
MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag); MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag);
if (_suspend_all) { if (suspend_all()) {
_nthreads_stopped++; _nthreads_stopped++;
if (is_synchronized()) { if (is_synchronized()) {
if (ConcGCYieldTimeout > 0) { if (ConcGCYieldTimeout > 0) {
@ -82,7 +82,7 @@ void SuspendibleThreadSet::yield() {
// This yield completes the request, so inform the requestor. // This yield completes the request, so inform the requestor.
_synchronize_wakeup->signal(); _synchronize_wakeup->signal();
} }
while (_suspend_all) { while (suspend_all()) {
ml.wait(); ml.wait();
} }
assert(_nthreads_stopped > 0, "Invalid"); assert(_nthreads_stopped > 0, "Invalid");
@ -97,8 +97,8 @@ void SuspendibleThreadSet::synchronize() {
} }
{ {
MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag); MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag);
assert(!_suspend_all, "Only one at a time"); assert(!suspend_all(), "Only one at a time");
_suspend_all = true; Atomic::store(&_suspend_all, true);
if (is_synchronized()) { if (is_synchronized()) {
return; return;
} }
@ -120,7 +120,7 @@ void SuspendibleThreadSet::synchronize() {
#ifdef ASSERT #ifdef ASSERT
MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag); MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag);
assert(_suspend_all, "STS not synchronizing"); assert(suspend_all(), "STS not synchronizing");
assert(is_synchronized(), "STS not synchronized"); assert(is_synchronized(), "STS not synchronized");
#endif #endif
} }
@ -128,8 +128,8 @@ void SuspendibleThreadSet::synchronize() {
void SuspendibleThreadSet::desynchronize() { void SuspendibleThreadSet::desynchronize() {
assert(Thread::current()->is_VM_thread(), "Must be the VM thread"); assert(Thread::current()->is_VM_thread(), "Must be the VM thread");
MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag); MonitorLocker ml(STS_lock, Mutex::_no_safepoint_check_flag);
assert(_suspend_all, "STS not synchronizing"); assert(suspend_all(), "STS not synchronizing");
assert(is_synchronized(), "STS not synchronized"); assert(is_synchronized(), "STS not synchronized");
_suspend_all = false; Atomic::store(&_suspend_all, false);
ml.notify_all(); ml.notify_all();
} }

8
src/hotspot/share/gc/shared/suspendibleThreadSet.hpp
View file

@ -26,6 +26,7 @@
#define SHARE_GC_SHARED_SUSPENDIBLETHREADSET_HPP #define SHARE_GC_SHARED_SUSPENDIBLETHREADSET_HPP
#include "memory/allocation.hpp" #include "memory/allocation.hpp"
#include "runtime/atomic.hpp"
// A SuspendibleThreadSet is a set of threads that can be suspended. // A SuspendibleThreadSet is a set of threads that can be suspended.
// A thread can join and later leave the set, and periodically yield. // A thread can join and later leave the set, and periodically yield.
@ -40,9 +41,10 @@ class SuspendibleThreadSet : public AllStatic {
friend class SuspendibleThreadSetLeaver; friend class SuspendibleThreadSetLeaver;
private: private:
static volatile bool _suspend_all;
static uint _nthreads; static uint _nthreads;
static uint _nthreads_stopped; static uint _nthreads_stopped;
static bool _suspend_all;
static double _suspend_all_start; static double _suspend_all_start;
static bool is_synchronized(); static bool is_synchronized();
@ -53,9 +55,11 @@ private:
// Removes the current thread from the set. // Removes the current thread from the set.
static void leave(); static void leave();
static bool suspend_all() { return Atomic::load(&_suspend_all); }
public: public:
// Returns true if an suspension is in progress. // Returns true if an suspension is in progress.
static bool should_yield() { return _suspend_all; } static bool should_yield() { return suspend_all(); }
// Suspends the current thread if a suspension is in progress. // Suspends the current thread if a suspension is in progress.
static void yield(); static void yield();