1 files changed, 35 insertions, 17 deletions

diff --git a/runtime/monitor.cc b/runtime/monitor.cc
index 0f567053e5..3771877c9d 100644
--- a/runtime/monitor.cc
+++ b/runtime/monitor.cc
@@ -314,21 +314,34 @@ std::string Monitor::PrettyContentionInfo(const std::string& owner_name,
   return oss.str();
 }
 
+bool Monitor::TryLockLocked(Thread* self) {
+  if (owner_ == nullptr) {  // Unowned.
+    owner_ = self;
+    CHECK_EQ(lock_count_, 0);
+    // When debugging, save the current monitor holder for future
+    // acquisition failures to use in sampled logging.
+    if (lock_profiling_threshold_ != 0) {
+      locking_method_ = self->GetCurrentMethod(&locking_dex_pc_);
+    }
+  } else if (owner_ == self) {  // Recursive.
+    lock_count_++;
+  } else {
+    return false;
+  }
+  AtraceMonitorLock(self, GetObject(), false /* is_wait */);
+  return true;
+}
+
+bool Monitor::TryLock(Thread* self) {
+  MutexLock mu(self, monitor_lock_);
+  return TryLockLocked(self);
+}
+
 void Monitor::Lock(Thread* self) {
   MutexLock mu(self, monitor_lock_);
   while (true) {
-    if (owner_ == nullptr) {  // Unowned.
-      owner_ = self;
-      CHECK_EQ(lock_count_, 0);
-      // When debugging, save the current monitor holder for future
-      // acquisition failures to use in sampled logging.
-      if (lock_profiling_threshold_ != 0) {
-        locking_method_ = self->GetCurrentMethod(&locking_dex_pc_);
-      }
-      break;
-    } else if (owner_ == self) {  // Recursive.
-      lock_count_++;
-      break;
+    if (TryLockLocked(self)) {
+      return;
     }
     // Contended.
     const bool log_contention = (lock_profiling_threshold_ != 0);
@@ -430,8 +443,6 @@ void Monitor::Lock(Thread* self) {
     monitor_lock_.Lock(self);  // Reacquire locks in order.
     --num_waiters_;
   }
-
-  AtraceMonitorLock(self, GetObject(), false /* is_wait */);
 }
 
 static void ThrowIllegalMonitorStateExceptionF(const char* fmt, ...)
@@ -852,7 +863,7 @@ static mirror::Object* FakeUnlock(mirror::Object* obj)
   return obj;
 }
 
-mirror::Object* Monitor::MonitorEnter(Thread* self, mirror::Object* obj) {
+mirror::Object* Monitor::MonitorEnter(Thread* self, mirror::Object* obj, bool trylock) {
   DCHECK(self != nullptr);
   DCHECK(obj != nullptr);
   self->AssertThreadSuspensionIsAllowable();
@@ -898,6 +909,9 @@ mirror::Object* Monitor::MonitorEnter(Thread* self, mirror::Object* obj) {
             InflateThinLocked(self, h_obj, lock_word, 0);
           }
         } else {
+          if (trylock) {
+            return nullptr;
+          }
           // Contention.
           contention_count++;
           Runtime* runtime = Runtime::Current();
@@ -916,8 +930,12 @@ mirror::Object* Monitor::MonitorEnter(Thread* self, mirror::Object* obj) {
       }
       case LockWord::kFatLocked: {
         Monitor* mon = lock_word.FatLockMonitor();
-        mon->Lock(self);
-        return h_obj.Get();  // Success!
+        if (trylock) {
+          return mon->TryLock(self) ? h_obj.Get() : nullptr;
+        } else {
+          mon->Lock(self);
+          return h_obj.Get();  // Success!
+        }
       }
       case LockWord::kHashCode:
         // Inflate with the existing hashcode.