Avoid race in single thread suspension.
Don't allow more than one concurrent single thread suspension to avoid
potential cycles and deadlocks where threads try to suspend each other.
Bug: 16364458, 16354227
Change-Id: I907f1d5591a6aa5c241d37d6b4a34f968f98df77
diff --git a/runtime/native/dalvik_system_VMStack.cc b/runtime/native/dalvik_system_VMStack.cc
index cf31064..5f718ba 100644
--- a/runtime/native/dalvik_system_VMStack.cc
+++ b/runtime/native/dalvik_system_VMStack.cc
@@ -35,7 +35,12 @@
// Suspend thread to build stack trace.
soa.Self()->TransitionFromRunnableToSuspended(kNative);
bool timed_out;
- Thread* thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+ Thread* thread;
+ {
+ // Take suspend thread lock to avoid races with threads trying to suspend this one.
+ MutexLock mu(soa.Self(), *Locks::thread_list_suspend_thread_lock_);
+ thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+ }
if (thread != nullptr) {
// Must be runnable to create returned array.
CHECK_EQ(soa.Self()->TransitionFromSuspendedToRunnable(), kNative);