提交 8ca53883 编写于 作者: D dcubed

8007476: assert(the_owner != NULL) failed: Did not find owning Java thread for lock word address

Summary: Make deadlock detection a little more robust in the case of being unable to find the JavaThread associated with an object lock.
Reviewed-by: sla, acorn
上级 4fbeb8df
......@@ -997,13 +997,19 @@ JvmtiEnvBase::get_object_monitor_usage(JavaThread* calling_thread, jobject objec
// move our object at this point. However, our owner value is safe
// since it is either the Lock word on a stack or a JavaThread *.
owning_thread = Threads::owning_thread_from_monitor_owner(owner, !at_safepoint);
assert(owning_thread != NULL, "sanity check");
if (owning_thread != NULL) { // robustness
// Cannot assume (owning_thread != NULL) here because this function
// may not have been called at a safepoint and the owning_thread
// might not be suspended.
if (owning_thread != NULL) {
// The monitor's owner either has to be the current thread, at safepoint
// or it has to be suspended. Any of these conditions will prevent both
// contending and waiting threads from modifying the state of
// the monitor.
if (!at_safepoint && !JvmtiEnv::is_thread_fully_suspended(owning_thread, true, &debug_bits)) {
// Don't worry! This return of JVMTI_ERROR_THREAD_NOT_SUSPENDED
// will not make it back to the JVM/TI agent. The error code will
// get intercepted in JvmtiEnv::GetObjectMonitorUsage() which
// will retry the call via a VM_GetObjectMonitorUsage VM op.
return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
}
HandleMark hm;
......
......@@ -813,6 +813,7 @@ JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) {
}
if (owner != NULL) {
// owning_thread_from_monitor_owner() may also return NULL here
return Threads::owning_thread_from_monitor_owner(owner, doLock);
}
......
......@@ -4285,7 +4285,9 @@ JavaThread *Threads::owning_thread_from_monitor_owner(address owner, bool doLock
if (owner == (address)p) return p;
}
}
assert(UseHeavyMonitors == false, "Did not find owning Java thread with UseHeavyMonitors enabled");
// Cannot assert on lack of success here since this function may be
// used by code that is trying to report useful problem information
// like deadlock detection.
if (UseHeavyMonitors) return NULL;
//
......@@ -4303,7 +4305,7 @@ JavaThread *Threads::owning_thread_from_monitor_owner(address owner, bool doLock
}
}
}
assert(the_owner != NULL, "Did not find owning Java thread for lock word address");
// cannot assert on lack of success here; see above comment
return the_owner;
}
......
/*
* Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
......@@ -327,8 +327,28 @@ DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(bool concurrent_locks)
while (waitingToLockMonitor != NULL || waitingToLockBlocker != NULL) {
cycle->add_thread(currentThread);
if (waitingToLockMonitor != NULL) {
currentThread = Threads::owning_thread_from_monitor_owner((address)waitingToLockMonitor->owner(),
currentThread = Threads::owning_thread_from_monitor_owner(
(address)waitingToLockMonitor->owner(),
false /* no locking needed */);
if (currentThread == NULL) {
// This function is called at a safepoint so the JavaThread
// that owns waitingToLockMonitor should be findable, but
// if it is not findable, then the previous currentThread is
// blocked permanently. We record this as a deadlock.
num_deadlocks++;
cycle->set_deadlock(true);
// add this cycle to the deadlocks list
if (deadlocks == NULL) {
deadlocks = cycle;
} else {
last->set_next(cycle);
}
last = cycle;
cycle = new DeadlockCycle();
break;
}
} else {
if (concurrent_locks) {
if (waitingToLockBlocker->is_a(SystemDictionary::abstract_ownable_synchronizer_klass())) {
......@@ -841,7 +861,17 @@ void DeadlockCycle::print_on(outputStream* st) const {
owner_desc = " (JVMTI raw monitor),\n which is held by";
}
currentThread = Threads::owning_thread_from_monitor_owner(
(address)waitingToLockMonitor->owner(), false /* no locking needed */);
(address)waitingToLockMonitor->owner(),
false /* no locking needed */);
if (currentThread == NULL) {
// The deadlock was detected at a safepoint so the JavaThread
// that owns waitingToLockMonitor should be findable, but
// if it is not findable, then the previous currentThread is
// blocked permanently.
st->print("%s UNKNOWN_owner_addr=" PTR_FORMAT, owner_desc,
(address)waitingToLockMonitor->owner());
continue;
}
} else {
st->print(" waiting for ownable synchronizer " INTPTR_FORMAT ", (a %s)",
(address)waitingToLockBlocker,
......
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