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8373100: Genshen: Control thread can miss allocation failure notification

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Reviewed-by: ysr, kdnilsen, xpeng
This commit is contained in:
William Kemper 2025-12-15 15:52:01 +00:00
parent 34f241317e
commit ea6493c4e1
2 changed files with 15 additions and 19 deletions
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23
src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp
View File

@ -96,8 +96,7 @@ void ShenandoahGenerationalControlThread::stop_service() {
log_debug(gc, thread)("Stopping control thread");
MonitorLocker ml(&_control_lock, Mutex::_no_safepoint_check_flag);
_heap->cancel_gc(GCCause::_shenandoah_stop_vm);
_requested_gc_cause = GCCause::_shenandoah_stop_vm;
notify_cancellation(ml, GCCause::_shenandoah_stop_vm);
notify_control_thread(ml, GCCause::_shenandoah_stop_vm);
// We can't wait here because it may interfere with the active cycle's ability
// to reach a safepoint (this runs on a java thread).
}
@ -140,7 +139,8 @@ void ShenandoahGenerationalControlThread::check_for_request(ShenandoahGCRequest&
}
ShenandoahGenerationalControlThread::GCMode ShenandoahGenerationalControlThread::prepare_for_allocation_failure_gc(ShenandoahGCRequest &request) {
// Important: not all paths update the request.generation. This is intentional.
// A degenerated cycle must use the same generation carried over from the previous request.
if (_degen_point == ShenandoahGC::_degenerated_unset) {
_degen_point = ShenandoahGC::_degenerated_outside_cycle;
request.generation = _heap->young_generation();
@ -633,9 +633,7 @@ void ShenandoahGenerationalControlThread::service_stw_degenerated_cycle(const Sh
void ShenandoahGenerationalControlThread::request_gc(GCCause::Cause cause) {
if (ShenandoahCollectorPolicy::is_allocation_failure(cause)) {
// GC should already be cancelled. Here we are just notifying the control thread to
// wake up and handle the cancellation request, so we don't need to set _requested_gc_cause.
notify_cancellation(cause);
notify_control_thread(cause);
} else if (ShenandoahCollectorPolicy::should_handle_requested_gc(cause)) {
handle_requested_gc(cause);
}
@ -661,7 +659,7 @@ bool ShenandoahGenerationalControlThread::request_concurrent_gc(ShenandoahGenera
log_info(gc)("Preempting old generation mark to allow %s GC", generation->name());
while (gc_mode() == servicing_old) {
ShenandoahHeap::heap()->cancel_gc(GCCause::_shenandoah_concurrent_gc);
notify_cancellation(ml, GCCause::_shenandoah_concurrent_gc);
notify_control_thread(ml, GCCause::_shenandoah_concurrent_gc);
ml.wait();
}
return true;
@ -701,14 +699,15 @@ void ShenandoahGenerationalControlThread::notify_control_thread(MonitorLocker& m
ml.notify();
}
void ShenandoahGenerationalControlThread::notify_cancellation(GCCause::Cause cause) {
void ShenandoahGenerationalControlThread::notify_control_thread(GCCause::Cause cause) {
MonitorLocker ml(&_control_lock, Mutex::_no_safepoint_check_flag);
notify_cancellation(ml, cause);
notify_control_thread(ml, cause);
}
void ShenandoahGenerationalControlThread::notify_cancellation(MonitorLocker& ml, GCCause::Cause cause) {
assert(_heap->cancelled_gc(), "GC should already be cancelled");
log_debug(gc,thread)("Notify control (%s): %s", gc_mode_name(gc_mode()), GCCause::to_string(cause));
void ShenandoahGenerationalControlThread::notify_control_thread(MonitorLocker& ml, GCCause::Cause cause) {
assert(_control_lock.is_locked(), "Request lock must be held here");
log_debug(gc, thread)("Notify control (%s): %s", gc_mode_name(gc_mode()), GCCause::to_string(cause));
_requested_gc_cause = cause;
ml.notify();
}

11
src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.hpp
View File

@ -135,16 +135,13 @@ private:
// Return printable name for the given gc mode.
static const char* gc_mode_name(GCMode mode);
// Takes the request lock and updates the requested cause and generation, then notifies the control thread.
// The overloaded variant should be used when the _control_lock is already held.
// These notify the control thread after updating _requested_gc_cause and (optionally) _requested_generation.
// Updating the requested generation is not necessary for allocation failures nor when stopping the thread.
void notify_control_thread(GCCause::Cause cause);
void notify_control_thread(MonitorLocker& ml, GCCause::Cause cause);
void notify_control_thread(GCCause::Cause cause, ShenandoahGeneration* generation);
void notify_control_thread(MonitorLocker& ml, GCCause::Cause cause, ShenandoahGeneration* generation);
// Notifies the control thread, but does not update the requested cause or generation.
// The overloaded variant should be used when the _control_lock is already held.
void notify_cancellation(GCCause::Cause cause);
void notify_cancellation(MonitorLocker& ml, GCCause::Cause cause);
// Configure the heap to age objects and regions if the aging period has elapsed.
void maybe_set_aging_cycle();