From 8bc6a58df7046b4d6f4b51eb274c7e60fea396ff Mon Sep 17 00:00:00 2001 From: Hans Boehm Date: Tue, 19 Dec 2023 18:48:15 +0000 Subject: 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 --- openjdkjvmti/ti_thread.cc | 54 +++++++++++++++++++---------------------------- 1 file changed, 22 insertions(+), 32 deletions(-) (limited to 'openjdkjvmti/ti_thread.cc') 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 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 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 thread_list = art::Runtime::Current()->GetThreadList()->GetList(); - // We have to be careful with threads exiting while we build this list. - std::vector tefs(thread_list.size()); - auto i = tefs.begin(); - for (art::Thread* thd : thread_list) { - thd->NotifyOnThreadExit(&*i++); - } - DCHECK(i == tefs.end()); std::vector> 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 peer = thread->LockedGetPeerFromOtherThread(tef); - if (peer != nullptr) { - peers.push_back(peer); - } + // Skip threads that are still starting. + if (thread->IsStillStarting()) { + continue; + } + + art::ObjPtr 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(data); - for (size_t j = 0; j != peers.size(); ++j) { - threads[j] = soa.AddLocalReference(peers[j]); + for (size_t i = 0; i != peers.size(); ++i) { + threads[i] = soa.AddLocalReference(peers[i]); } *threads_count_ptr = static_cast(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 -- cgit v1.2.3-59-g8ed1b