ThreadList::Dump() fix am: 764be11a8f am: 5ee1d74cb3

Original change: https://android-review.googlesource.com/c/platform/art/+/3472429

Change-Id: Id14be59e65eb67b70405b30d9c00a3208d73077b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

2 files changed, 13 insertions, 7 deletions

diff --git a/runtime/thread_list.cc b/runtime/thread_list.cc
index 6a8a7f566c..2acf58bfce 100644
--- a/runtime/thread_list.cc
+++ b/runtime/thread_list.cc
@@ -253,13 +253,16 @@ void ThreadList::Dump(std::ostream& os, bool dump_native_stack) {
     os << "DALVIK THREADS (" << list_.size() << "):\n";
   }
   if (self != nullptr) {
+    // Dump() can be called in any mutator lock state.
+    bool mutator_lock_held = Locks::mutator_lock_->IsSharedHeld(self);
     DumpCheckpoint checkpoint(dump_native_stack);
     // Acquire mutator lock separately for each thread, to avoid long runnable code sequence
     // without suspend checks.
-    size_t threads_running_checkpoint = RunCheckpoint(&checkpoint,
-                                                      nullptr,
-                                                      true,
-                                                      /* acquire_mutator_lock= */ true);
+    size_t threads_running_checkpoint =
+        RunCheckpoint(&checkpoint,
+                      nullptr,
+                      true,
+                      /* acquire_mutator_lock= */ !mutator_lock_held);
     if (threads_running_checkpoint != 0) {
       checkpoint.WaitForThreadsToRunThroughCheckpoint(threads_running_checkpoint);
     }
diff --git a/runtime/thread_list.h b/runtime/thread_list.h
index 4bf08dc9c1..8312282ed5 100644
--- a/runtime/thread_list.h
+++ b/runtime/thread_list.h
@@ -62,11 +62,14 @@ class ThreadList {
 
   void ShutDown();
 
-  void DumpForSigQuit(std::ostream& os)
-      REQUIRES(!Locks::thread_list_lock_, !Locks::mutator_lock_);
-  // For thread suspend timeout dumps.
+  // Dump stacks for all threads.
+  // This version includes some additional data.
+  void DumpForSigQuit(std::ostream& os) REQUIRES(!Locks::thread_list_lock_, !Locks::mutator_lock_);
+
+  // This version is less jank-prone if mutator_lock_ is not held.
   EXPORT void Dump(std::ostream& os, bool dump_native_stack = true)
       REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_);
+
   pid_t GetLockOwner();  // For SignalCatcher.
 
   // Thread suspension support.