Merge "Fix race in AllocEntrypointsInstrumented"

2 files changed, 11 insertions, 2 deletions

diff --git a/runtime/instrumentation.cc b/runtime/instrumentation.cc
index b107b72b55..a0c6bfbd83 100644
--- a/runtime/instrumentation.cc
+++ b/runtime/instrumentation.cc
@@ -83,7 +83,8 @@ Instrumentation::Instrumentation()
       deoptimized_methods_lock_("deoptimized methods lock"),
       deoptimization_enabled_(false),
       interpreter_handler_table_(kMainHandlerTable),
-      quick_alloc_entry_points_instrumentation_counter_(0) {
+      quick_alloc_entry_points_instrumentation_counter_(0),
+      alloc_entrypoints_instrumented_(false) {
 }
 
 void Instrumentation::InstallStubsForClass(mirror::Class* klass) {
@@ -642,10 +643,12 @@ void Instrumentation::SetEntrypointsInstrumented(bool instrumented) {
     MutexLock mu(self, *Locks::runtime_shutdown_lock_);
     SetQuickAllocEntryPointsInstrumented(instrumented);
     ResetQuickAllocEntryPoints();
+    alloc_entrypoints_instrumented_ = instrumented;
   } else {
     MutexLock mu(self, *Locks::runtime_shutdown_lock_);
     SetQuickAllocEntryPointsInstrumented(instrumented);
     ResetQuickAllocEntryPoints();
+    alloc_entrypoints_instrumented_ = instrumented;
   }
 }
 
diff --git a/runtime/instrumentation.h b/runtime/instrumentation.h
index b3cdb410f3..d07f47bf29 100644
--- a/runtime/instrumentation.h
+++ b/runtime/instrumentation.h
@@ -422,7 +422,7 @@ class Instrumentation {
   // Does not hold lock, used to check if someone changed from not instrumented to instrumented
   // during a GC suspend point.
   bool AllocEntrypointsInstrumented() const SHARED_REQUIRES(Locks::mutator_lock_) {
-    return quick_alloc_entry_points_instrumentation_counter_ > 0;
+    return alloc_entrypoints_instrumented_;
   }
 
  private:
@@ -579,6 +579,12 @@ class Instrumentation {
 
   // Greater than 0 if quick alloc entry points instrumented.
   size_t quick_alloc_entry_points_instrumentation_counter_;
+
+  // alloc_entrypoints_instrumented_ is only updated with all the threads suspended, this is done
+  // to prevent races with the GC where the GC relies on thread suspension only see
+  // alloc_entrypoints_instrumented_ change during suspend points.
+  bool alloc_entrypoints_instrumented_;
+
   friend class InstrumentationTest;  // For GetCurrentInstrumentationLevel and ConfigureStubs.
 
   DISALLOW_COPY_AND_ASSIGN(Instrumentation);