Ensure that updates to the global event mask are atomic
We were setting and testing the global event mask in a way that
allowed races with other threads. This could cause issues if multiple
threads write to the mask at the same time and could cause changes to
the current event state to be missed.
Test: ./test.py --host -j50
Bug: 69657830
Change-Id: I5e2759af598e6179fd25fcbe6b211a9369217156
diff --git a/openjdkjvmti/events.cc b/openjdkjvmti/events.cc
index be4ebbc..a3d9bb4 100644
--- a/openjdkjvmti/events.cc
+++ b/openjdkjvmti/events.cc
@@ -139,7 +139,9 @@
}
-void EventMasks::EnableEvent(art::Thread* thread, ArtJvmtiEvent event) {
+void EventMasks::EnableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event) {
+ DCHECK_EQ(&env->event_masks, this);
+ env->event_info_mutex_.AssertExclusiveHeld(art::Thread::Current());
DCHECK(EventMask::EventIsInRange(event));
GetEventMask(thread).Set(event);
if (thread != nullptr) {
@@ -147,7 +149,9 @@
}
}
-void EventMasks::DisableEvent(art::Thread* thread, ArtJvmtiEvent event) {
+void EventMasks::DisableEvent(ArtJvmTiEnv* env, art::Thread* thread, ArtJvmtiEvent event) {
+ DCHECK_EQ(&env->event_masks, this);
+ env->event_info_mutex_.AssertExclusiveHeld(art::Thread::Current());
DCHECK(EventMask::EventIsInRange(event));
GetEventMask(thread).Set(event, false);
if (thread != nullptr) {
@@ -1131,20 +1135,28 @@
return ERR(MUST_POSSESS_CAPABILITY);
}
- bool old_state = global_mask.Test(event);
+ bool old_state;
+ bool new_state;
- if (mode == JVMTI_ENABLE) {
- env->event_masks.EnableEvent(thread, event);
- global_mask.Set(event);
- } else {
- DCHECK_EQ(mode, JVMTI_DISABLE);
+ {
+ // Change the event masks atomically.
+ art::Thread* self = art::Thread::Current();
+ art::MutexLock mu(self, envs_lock_);
+ art::WriterMutexLock mu_env_info(self, env->event_info_mutex_);
+ old_state = global_mask.Test(event);
+ if (mode == JVMTI_ENABLE) {
+ env->event_masks.EnableEvent(env, thread, event);
+ global_mask.Set(event);
+ new_state = true;
+ } else {
+ DCHECK_EQ(mode, JVMTI_DISABLE);
- env->event_masks.DisableEvent(thread, event);
- RecalculateGlobalEventMask(event);
+ env->event_masks.DisableEvent(env, thread, event);
+ RecalculateGlobalEventMaskLocked(event);
+ new_state = global_mask.Test(event);
+ }
}
- bool new_state = global_mask.Test(event);
-
// Handle any special work required for the event type.
if (new_state != old_state) {
HandleEventType(event, mode == JVMTI_ENABLE);