--- a/hotspot/src/share/vm/runtime/thread.cpp Wed Mar 04 02:23:38 2015 +0100
+++ b/hotspot/src/share/vm/runtime/thread.cpp Thu Mar 05 17:27:16 2015 +0100
@@ -1201,8 +1201,15 @@
}
int WatcherThread::sleep() const {
+ // The WatcherThread does not participate in the safepoint protocol
+ // for the PeriodicTask_lock because it is not a JavaThread.
MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
+ if (_should_terminate) {
+ // check for termination before we do any housekeeping or wait
+ return 0; // we did not sleep.
+ }
+
// remaining will be zero if there are no tasks,
// causing the WatcherThread to sleep until a task is
// enrolled
@@ -1215,8 +1222,9 @@
jlong time_before_loop = os::javaTimeNanos();
- for (;;) {
- bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag, remaining);
+ while (true) {
+ bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
+ remaining);
jlong now = os::javaTimeNanos();
if (remaining == 0) {
@@ -1257,7 +1265,7 @@
this->initialize_thread_local_storage();
this->set_native_thread_name(this->name());
this->set_active_handles(JNIHandleBlock::allocate_block());
- while (!_should_terminate) {
+ while (true) {
assert(watcher_thread() == Thread::current(), "thread consistency check");
assert(watcher_thread() == this, "thread consistency check");
@@ -1293,6 +1301,11 @@
}
}
+ if (_should_terminate) {
+ // check for termination before posting the next tick
+ break;
+ }
+
PeriodicTask::real_time_tick(time_waited);
}
@@ -1323,27 +1336,19 @@
}
void WatcherThread::stop() {
- // Get the PeriodicTask_lock if we can. If we cannot, then the
- // WatcherThread is using it and we don't want to block on that lock
- // here because that might cause a safepoint deadlock depending on
- // what the current WatcherThread tasks are doing.
- bool have_lock = PeriodicTask_lock->try_lock();
-
- _should_terminate = true;
- OrderAccess::fence(); // ensure WatcherThread sees update in main loop
-
- if (have_lock) {
+ {
+ // Follow normal safepoint aware lock enter protocol since the
+ // WatcherThread is stopped by another JavaThread.
+ MutexLocker ml(PeriodicTask_lock);
+ _should_terminate = true;
+
WatcherThread* watcher = watcher_thread();
if (watcher != NULL) {
- // If we managed to get the lock, then we should unpark the
- // WatcherThread so that it can see we want it to stop.
+ // unpark the WatcherThread so it can see that it should terminate
watcher->unpark();
}
-
- PeriodicTask_lock->unlock();
}
- // it is ok to take late safepoints here, if needed
MutexLocker mu(Terminator_lock);
while (watcher_thread() != NULL) {
@@ -1363,9 +1368,7 @@
}
void WatcherThread::unpark() {
- MutexLockerEx ml(PeriodicTask_lock->owned_by_self()
- ? NULL
- : PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
+ assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
PeriodicTask_lock->notify();
}
@@ -3562,8 +3565,8 @@
}
{
- MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
- // Make sure the watcher thread can be started by WatcherThread::start()
+ MutexLocker ml(PeriodicTask_lock);
+ // Make sure the WatcherThread can be started by WatcherThread::start()
// or by dynamic enrollment.
WatcherThread::make_startable();
// Start up the WatcherThread if there are any periodic tasks