Revert "Revert^8 "Thread suspension cleanup and deadlock fix""

This reverts commit 221b6c5fcd66d4b6f2626c311d03bde2fb1589f9.

Reason for revert: Preemptive revert. Earlier versions have had a tendency to cause subtle breakage.

Please do not submit unless something breaks.

Change-Id: Iad2a7f920756f365789c422948632f5db5a28fd5

1 files changed, 11 insertions, 18 deletions

diff --git a/runtime/native/dalvik_system_VMStack.cc b/runtime/native/dalvik_system_VMStack.cc
index bf441b4b1d..71078c9ad2 100644
--- a/runtime/native/dalvik_system_VMStack.cc
+++ b/runtime/native/dalvik_system_VMStack.cc
@@ -48,29 +48,19 @@ static ResultT GetThreadStack(const ScopedFastNativeObjectAccess& soa,
   } else {
     // Never allow suspending the heap task thread since it may deadlock if allocations are
     // required for the stack trace.
-    Thread* heap_task_thread = nullptr;
-    for (int i = 0; i < 20; ++i) {
-      heap_task_thread = Runtime::Current()->GetHeap()->GetTaskProcessor()->GetRunningThread();
-      if (heap_task_thread != nullptr) {
-        break;
-      }
-      // heap_task_thread could be null if the daemons aren't fully running yet.  But it can appear
-      // in enumerations, and thus we could try to get its stack even before that. Try to wait
-      // for a non-null value so we can avoid suspending it.
-      static constexpr int kHeapTaskDaemonSleepMicros = 5000;
-      usleep(kHeapTaskDaemonSleepMicros);
-    }
-    if (heap_task_thread == nullptr) {
-      LOG(ERROR) << "No HeapTaskDaemon; refusing to get thread stack.";
-      return nullptr;
-    }
-    if (decoded_peer == heap_task_thread->GetPeerFromOtherThread()) {
+    Thread* heap_task_thread =
+        Runtime::Current()->GetHeap()->GetTaskProcessor()->GetRunningThread();
+    // heap_task_thread could be null if the daemons aren't yet started.
+    if (heap_task_thread != nullptr && decoded_peer == heap_task_thread->GetPeerFromOtherThread()) {
       return nullptr;
     }
     // Suspend thread to build stack trace.
     ScopedThreadSuspension sts(soa.Self(), ThreadState::kNative);
     ThreadList* thread_list = Runtime::Current()->GetThreadList();
-    Thread* thread = thread_list->SuspendThreadByPeer(peer, SuspendReason::kInternal);
+    bool timed_out;
+    Thread* thread = thread_list->SuspendThreadByPeer(peer,
+                                                      SuspendReason::kInternal,
+                                                      &timed_out);
     if (thread != nullptr) {
       // Must be runnable to create returned array.
       {
@@ -80,6 +70,9 @@ static ResultT GetThreadStack(const ScopedFastNativeObjectAccess& soa,
       // Restart suspended thread.
       bool resumed = thread_list->Resume(thread, SuspendReason::kInternal);
       DCHECK(resumed);
+    } else if (timed_out) {
+      LOG(ERROR) << "Trying to get thread's stack failed as the thread failed to suspend within a "
+          "generous timeout.";
     }
   }
   return trace;