From 17195424dd56070a773e82ab5430c788e54a78c6 Mon Sep 17 00:00:00 2001
From: Hans Boehm <hboehm@google.com>
Date: Tue, 19 Dec 2023 20:35:24 +0000
Subject: Revert^18 "Thread suspension cleanup and deadlock fix"

This reverts commit 8bc6a58df7046b4d6f4b51eb274c7e60fea396ff.

PS1 is identical to
  https://android-review.git.corp.google.com/c/platform/art/+/2746640

PS2 makes the following changes:
- Remove one DCHECK each from the two WaitForFlipFunction variants.
  The DCHECK could fail if another GC was started in the interim.
- Break up the WaitForSuspendBarrier timeout into shorter ones.
  so we don't time out as easily if our process is frozen.
- Include the thread name for ThreadSuspendByThreadIdWarning, since
  we don't get complete tombstones for some failures.

Test: Treehugger, host tests.
Bug: 240742796
Bug: 203363895
Bug: 238032384
Bug: 253671779
Bug: 276660630
Bug: 295880862
Bug: 294334417
Bug: 301090887
Bug: 313347640
(and more)

Change-Id: I12c5c01b1e006baab4ee4148aadbc721723fb89e
---
 runtime/gc/task_processor.cc | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

(limited to 'runtime/gc/task_processor.cc')

diff --git a/runtime/gc/task_processor.cc b/runtime/gc/task_processor.cc
index 494cf2bb79..e56dbd17c3 100644
--- a/runtime/gc/task_processor.cc
+++ b/runtime/gc/task_processor.cc
@@ -103,9 +103,31 @@ bool TaskProcessor::IsRunning() const {
   return is_running_;
 }
 
-Thread* TaskProcessor::GetRunningThread() const {
-  MutexLock mu(Thread::Current(), lock_);
-  return running_thread_;
+bool TaskProcessor::WaitForThread(Thread* self) {
+  // Waiting for too little time here may cause us to fail to get stack traces, since we can't
+  // safely do so without identifying a HeapTaskDaemon to avoid it. Waiting too long could
+  // conceivably deadlock if we somehow try to get a stack trace on the way to starting the
+  // HeapTaskDaemon. Under normal circumstances. this should terminate immediately, since
+  // HeapTaskDaemon should normally be running.
+  constexpr int kTotalWaitMillis = 100;
+  for (int i = 0; i < kTotalWaitMillis; ++i) {
+    if (is_running_) {
+      return true;
+    }
+    cond_.TimedWait(self, 1 /*msecs*/, 0 /*nsecs*/);
+  }
+  LOG(ERROR) << "No identifiable HeapTaskDaemon; unsafe to get thread stacks.";
+  return false;
+}
+
+bool TaskProcessor::IsRunningThread(Thread* t, bool wait) {
+  Thread* self = Thread::Current();
+  MutexLock mu(self, lock_);
+  if (wait && !WaitForThread(self)) {
+    // If Wait failed, either answer may be correct; in our case, true is safer.
+    return true;
+  }
+  return running_thread_ == t;
 }
 
 void TaskProcessor::Stop(Thread* self) {
-- 
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