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8210832: Remove sneaky locking in class Monitor

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Removed sneaky locking and simplified vm monitors implementation

Co-authored-by: David Holmes <david.holmes@oracle.com>
Reviewed-by: rehn, dcubed, pliden, dholmes, coleenp
This commit is contained in:
Patricio Chilano Mateo 2019-02-05 15:12:13 -05:00
parent cd9b1aabb0
commit c94cdddbdd
17 changed files with 509 additions and 1157 deletions
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43
src/hotspot/share/runtime/safepoint.cpp
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@ -793,7 +793,7 @@ void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, Ja
// -------------------------------------------------------------------------------------------------------
// Implementation of Safepoint callback point
void SafepointSynchronize::block(JavaThread *thread) {
void SafepointSynchronize::block(JavaThread *thread, bool block_in_safepoint_check) {
assert(thread != NULL, "thread must be set");
assert(thread->is_Java_thread(), "not a Java thread");
@ -848,28 +848,37 @@ void SafepointSynchronize::block(JavaThread *thread) {
}
}
// We transition the thread to state _thread_blocked here, but
// we can't do our usual check for external suspension and then
// self-suspend after the lock_without_safepoint_check() call
// below because we are often called during transitions while
// we hold different locks. That would leave us suspended while
// holding a resource which results in deadlocks.
thread->set_thread_state(_thread_blocked);
Safepoint_lock->unlock();
if (block_in_safepoint_check) {
// We transition the thread to state _thread_blocked here, but
// we can't do our usual check for external suspension and then
// self-suspend after the lock_without_safepoint_check() call
// below because we are often called during transitions while
// we hold different locks. That would leave us suspended while
// holding a resource which results in deadlocks.
thread->set_thread_state(_thread_blocked);
Safepoint_lock->unlock();
// We now try to acquire the threads lock. Since this lock is hold by the VM thread during
// the entire safepoint, the threads will all line up here during the safepoint.
Threads_lock->lock_without_safepoint_check();
// restore original state. This is important if the thread comes from compiled code, so it
// will continue to execute with the _thread_in_Java state.
thread->set_thread_state(state);
Threads_lock->unlock();
// We now try to acquire the threads lock. Since this lock is hold by the VM thread during
// the entire safepoint, the threads will all line up here during the safepoint.
Threads_lock->lock_without_safepoint_check();
// restore original state. This is important if the thread comes from compiled code, so it
// will continue to execute with the _thread_in_Java state.
thread->set_thread_state(state);
Threads_lock->unlock();
} else {
// We choose not to block in this call since we would be
// caught when transitioning back anyways if the safepoint
// is still going on.
thread->set_thread_state(state);
Safepoint_lock->unlock();
}
break;
case _thread_in_native_trans:
case _thread_blocked_trans:
case _thread_new_trans:
if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back &&
block_in_safepoint_check) {
thread->print_thread_state();
fatal("Deadlock in safepoint code. "
"Should have called back to the VM before blocking.");