Revert^17 "Thread suspension cleanup and deadlock fix"

This reverts commit c6371b52df0da31acc174a3526274417b7aac0a7.

Reason for revert: This seems to have two remaining issues:

1. The second DCHECK in WaitForFlipFunction is not completely guaranteed to hold, resulting in failures for 658-fp-read-barrier.
2. WaitForSuspendBarrier seems to time out occasionally, possibly spuriously so. We fail when the futex times out once. That's probably incompatible with the app freezer. We should retry a few times.

Change-Id: Ibd8909b31083fc29e6d4f1fcde003d08eb16fc0a

1 files changed, 22 insertions, 32 deletions

diff --git a/openjdkjvmti/ti_thread.cc b/openjdkjvmti/ti_thread.cc
index 191b63c050..13eebbff04 100644
--- a/openjdkjvmti/ti_thread.cc
+++ b/openjdkjvmti/ti_thread.cc
@@ -289,9 +289,7 @@ jvmtiError ThreadUtil::GetThreadInfo(jvmtiEnv* env, jthread thread, jvmtiThreadI
 
     info_ptr->is_daemon = target->IsDaemon();
 
-    art::ObjPtr<art::mirror::Object> peer = target->LockedGetPeerFromOtherThread();
-    // *target may be invalid here since we may have temporarily released thread_list_lock_.
-    target = nullptr;  // Value should not be used.
+    art::ObjPtr<art::mirror::Object> peer = target->GetPeerFromOtherThread();
 
     // ThreadGroup.
     if (peer != nullptr) {
@@ -549,7 +547,6 @@ static jint GetJavaStateFromInternal(const InternalThreadState& state) {
 
 // Suspends the current thread if it has any suspend requests on it.
 void ThreadUtil::SuspendCheck(art::Thread* self) {
-  DCHECK(!self->ReadFlag(art::ThreadFlag::kSuspensionImmune));
   art::ScopedObjectAccess soa(self);
   // Really this is only needed if we are in FastJNI and actually have the mutator_lock_ already.
   self->FullSuspendCheck();
@@ -643,30 +640,20 @@ jvmtiError ThreadUtil::GetAllThreads(jvmtiEnv* env,
 
   art::MutexLock mu(current, *art::Locks::thread_list_lock_);
   std::list<art::Thread*> thread_list = art::Runtime::Current()->GetThreadList()->GetList();
-  // We have to be careful with threads exiting while we build this list.
-  std::vector<art::ThreadExitFlag> tefs(thread_list.size());
-  auto i = tefs.begin();
-  for (art::Thread* thd : thread_list) {
-    thd->NotifyOnThreadExit(&*i++);
-  }
-  DCHECK(i == tefs.end());
 
   std::vector<art::ObjPtr<art::mirror::Object>> peers;
 
-  i = tefs.begin();
   for (art::Thread* thread : thread_list) {
-    art::ThreadExitFlag* tef = &*i++;
-    // Skip threads that have since exited or are still starting.
-    if (!tef->HasExited() && !thread->IsStillStarting()) {
-      // LockedGetPeerFromOtherThreads() may release lock!
-      art::ObjPtr<art::mirror::Object> peer = thread->LockedGetPeerFromOtherThread(tef);
-      if (peer != nullptr) {
-        peers.push_back(peer);
-      }
+    // Skip threads that are still starting.
+    if (thread->IsStillStarting()) {
+      continue;
+    }
+
+    art::ObjPtr<art::mirror::Object> peer = thread->GetPeerFromOtherThread();
+    if (peer != nullptr) {
+      peers.push_back(peer);
     }
-    thread->UnregisterThreadExitFlag(tef);
   }
-  DCHECK(i == tefs.end());
 
   if (peers.empty()) {
     *threads_count_ptr = 0;
@@ -678,8 +665,8 @@ jvmtiError ThreadUtil::GetAllThreads(jvmtiEnv* env,
       return data_result;
     }
     jthread* threads = reinterpret_cast<jthread*>(data);
-    for (size_t j = 0; j != peers.size(); ++j) {
-      threads[j] = soa.AddLocalReference<jthread>(peers[j]);
+    for (size_t i = 0; i != peers.size(); ++i) {
+      threads[i] = soa.AddLocalReference<jthread>(peers[i]);
     }
 
     *threads_count_ptr = static_cast<jint>(peers.size());
@@ -913,13 +900,17 @@ jvmtiError ThreadUtil::SuspendOther(art::Thread* self,
         }
       }
     }
+    bool timeout = true;
     art::Thread* ret_target = art::Runtime::Current()->GetThreadList()->SuspendThreadByPeer(
-        target_jthread, art::SuspendReason::kForUserCode);
-    if (ret_target == nullptr) {
+        target_jthread,
+        art::SuspendReason::kForUserCode,
+        &timeout);
+    if (ret_target == nullptr && !timeout) {
       // TODO It would be good to get more information about why exactly the thread failed to
       // suspend.
       return ERR(INTERNAL);
-    } else {
+    } else if (!timeout) {
+      // we didn't time out and got a result.
       return OK;
     }
     // We timed out. Just go around and try again.
@@ -936,11 +927,10 @@ jvmtiError ThreadUtil::SuspendSelf(art::Thread* self) {
       // This can only happen if we race with another thread to suspend 'self' and we lose.
       return ERR(THREAD_SUSPENDED);
     }
-    {
-      // IncrementSuspendCount normally needs thread_list_lock_ to ensure the thread stays
-      // around. In this case we are the target thread, so we fake it.
-      art::FakeMutexLock fmu(*art::Locks::thread_list_lock_);
-      self->IncrementSuspendCount(self, nullptr, nullptr, art::SuspendReason::kForUserCode);
+    // We shouldn't be able to fail this.
+    if (!self->ModifySuspendCount(self, +1, nullptr, art::SuspendReason::kForUserCode)) {
+      // TODO More specific error would be nice.
+      return ERR(INTERNAL);
     }
   }
   // Once we have requested the suspend we actually go to sleep. We need to do this after releasing