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6983311: G1: LoopTest hangs when run with -XX:+ExplicitInvokesConcurrent

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Clear the concurrent marking "in progress" flag while the FullGCCount_lock is held. This avoids a race that can cause back to back System.gc() calls, when ExplicitGCInvokesConcurrent is enabled, to fail to initiate a marking cycle causing the requesting thread to hang.

Reviewed-by: tonyp, ysr
This commit is contained in:
John Cuthbertson 2010-10-01 18:23:16 -07:00
parent 603e50f355
commit 20289fbffd
3 changed files with 14 additions and 5 deletions
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3
hotspot/src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp
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@ -303,9 +303,10 @@ void ConcurrentMarkThread::print_on(outputStream* st) const {
}
void ConcurrentMarkThread::sleepBeforeNextCycle() {
clear_in_progress();
// We join here because we don't want to do the "shouldConcurrentMark()"
// below while the world is otherwise stopped.
assert(!in_progress(), "should have been cleared");
MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
while (!started()) {
CGC_lock->wait(Mutex::_no_safepoint_check_flag);

8
hotspot/src/share/vm/gc_implementation/g1/concurrentMarkThread.hpp
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@ -69,12 +69,12 @@ class ConcurrentMarkThread: public ConcurrentGCThread {
ConcurrentMark* cm() { return _cm; }
void set_started() { _started = true; }
void clear_started() { _started = false; }
void set_started() { assert(!_in_progress, "cycle in progress"); _started = true; }
void clear_started() { assert(_in_progress, "must be starting a cycle"); _started = false; }
bool started() { return _started; }
void set_in_progress() { _in_progress = true; }
void clear_in_progress() { _in_progress = false; }
void set_in_progress() { assert(_started, "must be starting a cycle"); _in_progress = true; }
void clear_in_progress() { assert(!_started, "must not be starting a new cycle"); _in_progress = false; }
bool in_progress() { return _in_progress; }
// This flag returns true from the moment a marking cycle is

8
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
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@ -1785,6 +1785,14 @@ void G1CollectedHeap::increment_full_collections_completed(bool outer) {
_full_collections_completed += 1;
// We need to clear the "in_progress" flag in the CM thread before
// we wake up any waiters (especially when ExplicitInvokesConcurrent
// is set) so that if a waiter requests another System.gc() it doesn't
// incorrectly see that a marking cyle is still in progress.
if (outer) {
_cmThread->clear_in_progress();
}
// This notify_all() will ensure that a thread that called
// System.gc() with (with ExplicitGCInvokesConcurrent set or not)
// and it's waiting for a full GC to finish will be woken up. It is