Fix the empty checkpoint timeout.

The problem happens when a thread is indirectly blocked on a mutex
that another thread holds and is blocked on a weak ref access.

Add a way to do a dummy wakeup on a thread that's blocked on a mutex
so that the thread will respond to the empty checkpoint request. Do
this for the mutexes that are expected to be held when a weak ref is
accessed. Add a check that detects an unexpected case.

Bug: 33006388
Bug: 12687968
Test: test-art-host.
Change-Id: Iefec69b9a21aa25a928cb31fcf4fb872f867a8c2

1 files changed, 2 insertions, 2 deletions

diff --git a/runtime/gc/reference_processor.cc b/runtime/gc/reference_processor.cc
index c1548365c7..86b152211c 100644
--- a/runtime/gc/reference_processor.cc
+++ b/runtime/gc/reference_processor.cc
@@ -104,7 +104,7 @@ ObjPtr<mirror::Object> ReferenceProcessor::GetReferent(Thread* self,
     }
     // Check and run the empty checkpoint before blocking so the empty checkpoint will work in the
     // presence of threads blocking for weak ref access.
-    self->CheckEmptyCheckpoint();
+    self->CheckEmptyCheckpointFromWeakRefAccess(Locks::reference_processor_lock_);
     condition_.WaitHoldingLocks(self);
   }
   return reference->GetReferent();
@@ -292,7 +292,7 @@ void ReferenceProcessor::WaitUntilDoneProcessingReferences(Thread* self) {
          (kUseReadBarrier && !self->GetWeakRefAccessEnabled())) {
     // Check and run the empty checkpoint before blocking so the empty checkpoint will work in the
     // presence of threads blocking for weak ref access.
-    self->CheckEmptyCheckpoint();
+    self->CheckEmptyCheckpointFromWeakRefAccess(Locks::reference_processor_lock_);
     condition_.WaitHoldingLocks(self);
   }
 }