Revert "Revert "Use try lock to fix class resolution race""
Fix possible deadlock in EnsureResolved caused by interaction with
GC. Since we were sleeping while holding the mutator lock, it could
block thread suspension. This would deadlock if the thread that
had locked h_class is already suspended since we would spin forever
and not make progress.
Bug: 27417671
Bug: 30500547
Test: test-art-host ART_TEST_GC_STRESS=true
This reverts commit 69bf969c055c31a75d17ea92aeee756042678114.
Change-Id: Id8750df065dc3b9ef7dc874f2eb2cc2c58e5d1eb
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index d0dad64..9736573 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -2179,20 +2179,37 @@
}
// Wait for the class if it has not already been linked.
- if (!klass->IsResolved() && !klass->IsErroneous()) {
+ size_t index = 0;
+ // Maximum number of yield iterations until we start sleeping.
+ static const size_t kNumYieldIterations = 1000;
+ // How long each sleep is in us.
+ static const size_t kSleepDurationUS = 1000; // 1 ms.
+ while (!klass->IsResolved() && !klass->IsErroneous()) {
StackHandleScope<1> hs(self);
HandleWrapper<mirror::Class> h_class(hs.NewHandleWrapper(&klass));
- ObjectLock<mirror::Class> lock(self, h_class);
- // Check for circular dependencies between classes.
- if (!h_class->IsResolved() && h_class->GetClinitThreadId() == self->GetTid()) {
- ThrowClassCircularityError(h_class.Get());
- mirror::Class::SetStatus(h_class, mirror::Class::kStatusError, self);
- return nullptr;
+ {
+ ObjectTryLock<mirror::Class> lock(self, h_class);
+ // Can not use a monitor wait here since it may block when returning and deadlock if another
+ // thread has locked klass.
+ if (lock.Acquired()) {
+ // Check for circular dependencies between classes, the lock is required for SetStatus.
+ if (!h_class->IsResolved() && h_class->GetClinitThreadId() == self->GetTid()) {
+ ThrowClassCircularityError(h_class.Get());
+ mirror::Class::SetStatus(h_class, mirror::Class::kStatusError, self);
+ return nullptr;
+ }
+ }
}
- // Wait for the pending initialization to complete.
- while (!h_class->IsResolved() && !h_class->IsErroneous()) {
- lock.WaitIgnoringInterrupts();
+ {
+ // Handle wrapper deals with klass moving.
+ ScopedThreadSuspension sts(self, kSuspended);
+ if (index < kNumYieldIterations) {
+ sched_yield();
+ } else {
+ usleep(kSleepDurationUS);
+ }
}
+ ++index;
}
if (klass->IsErroneous()) {