Make empty checkpoint work while weak ref access is disabled.

Fix a potential race on PushOntoMarkStack for CC by running an empty
checkpoint (while weak ref access is disabled).

Bug: 32508093
Bug: 12687968
Test: test-art-host with CC/CMS, libartd boot with N9, Ritz EAAC.
Change-Id: I3749bb525e7734804307ee16262355f3fc730312

1 files changed, 6 insertions, 1 deletions

diff --git a/runtime/gc/reference_processor.cc b/runtime/gc/reference_processor.cc
index 798ecd3d87..2cde7d5731 100644
--- a/runtime/gc/reference_processor.cc
+++ b/runtime/gc/reference_processor.cc
@@ -55,7 +55,6 @@ void ReferenceProcessor::DisableSlowPath(Thread* self) {
 }
 
 void ReferenceProcessor::BroadcastForSlowPath(Thread* self) {
-  CHECK(kUseReadBarrier);
   MutexLock mu(self, *Locks::reference_processor_lock_);
   condition_.Broadcast(self);
 }
@@ -99,6 +98,9 @@ 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();
     condition_.WaitHoldingLocks(self);
   }
   return reference->GetReferent();
@@ -270,6 +272,9 @@ bool ReferenceProcessor::MakeCircularListIfUnenqueued(
   // Wait untul we are done processing reference.
   while ((!kUseReadBarrier && SlowPathEnabled()) ||
          (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();
     condition_.WaitHoldingLocks(self);
   }
   // At this point, since the sentinel of the reference is live, it is guaranteed to not be