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src/share/vm/gc_implementation/shared/suspendibleThreadSet.cpp@9f28a4cac6d9 (annotated)

src/share/vm/gc_implementation/shared/suspendibleThreadSet.cpp

Wed, 31 Jul 2019 14:28:51 -0400

author

kbarrett

date

Wed, 31 Jul 2019 14:28:51 -0400

changeset 9787

9f28a4cac6d9

parent 6906

581e70386ec9

permissions

-rw-r--r--

8048556: Unnecessary GCLocker-initiated young GCs
Summary: Fixed recognition of unnecessary GCLocker collections.
Reviewed-by: pliden, tschatzl
Contributed-by: johnc@azul.com

pliden@6906	1	/*
pliden@6906	2	* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
pliden@6906	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
pliden@6906	4	*
pliden@6906	5	* This code is free software; you can redistribute it and/or modify it
pliden@6906	6	* under the terms of the GNU General Public License version 2 only, as
pliden@6906	7	* published by the Free Software Foundation.
pliden@6906	8	*
pliden@6906	9	* This code is distributed in the hope that it will be useful, but WITHOUT
pliden@6906	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
pliden@6906	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
pliden@6906	12	* version 2 for more details (a copy is included in the LICENSE file that
pliden@6906	13	* accompanied this code).
pliden@6906	14	*
pliden@6906	15	* You should have received a copy of the GNU General Public License version
pliden@6906	16	* 2 along with this work; if not, write to the Free Software Foundation,
pliden@6906	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
pliden@6906	18	*
pliden@6906	19	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
pliden@6906	20	* or visit www.oracle.com if you need additional information or have any
pliden@6906	21	* questions.
pliden@6906	22	*
pliden@6906	23	*/
pliden@6906	24
pliden@6906	25	#include "precompiled.hpp"
pliden@6906	26	#include "gc_implementation/shared/suspendibleThreadSet.hpp"
pliden@6906	27	#include "runtime/mutexLocker.hpp"
pliden@6906	28	#include "runtime/thread.inline.hpp"
pliden@6906	29
pliden@6906	30	uint SuspendibleThreadSet::_nthreads = 0;
pliden@6906	31	uint SuspendibleThreadSet::_nthreads_stopped = 0;
pliden@6906	32	bool SuspendibleThreadSet::_suspend_all = false;
pliden@6906	33	double SuspendibleThreadSet::_suspend_all_start = 0.0;
pliden@6906	34
pliden@6906	35	void SuspendibleThreadSet::join() {
pliden@6906	36	MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
pliden@6906	37	while (_suspend_all) {
pliden@6906	38	ml.wait(Mutex::_no_safepoint_check_flag);
pliden@6906	39	}
pliden@6906	40	_nthreads++;
pliden@6906	41	}
pliden@6906	42
pliden@6906	43	void SuspendibleThreadSet::leave() {
pliden@6906	44	MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
pliden@6906	45	assert(_nthreads > 0, "Invalid");
pliden@6906	46	_nthreads--;
pliden@6906	47	if (_suspend_all) {
pliden@6906	48	ml.notify_all();
pliden@6906	49	}
pliden@6906	50	}
pliden@6906	51
pliden@6906	52	void SuspendibleThreadSet::yield() {
pliden@6906	53	if (_suspend_all) {
pliden@6906	54	MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
pliden@6906	55	if (_suspend_all) {
pliden@6906	56	_nthreads_stopped++;
pliden@6906	57	if (_nthreads_stopped == _nthreads) {
pliden@6906	58	if (ConcGCYieldTimeout > 0) {
pliden@6906	59	double now = os::elapsedTime();
pliden@6906	60	guarantee((now - _suspend_all_start) * 1000.0 < (double)ConcGCYieldTimeout, "Long delay");
pliden@6906	61	}
pliden@6906	62	}
pliden@6906	63	ml.notify_all();
pliden@6906	64	while (_suspend_all) {
pliden@6906	65	ml.wait(Mutex::_no_safepoint_check_flag);
pliden@6906	66	}
pliden@6906	67	assert(_nthreads_stopped > 0, "Invalid");
pliden@6906	68	_nthreads_stopped--;
pliden@6906	69	ml.notify_all();
pliden@6906	70	}
pliden@6906	71	}
pliden@6906	72	}
pliden@6906	73
pliden@6906	74	void SuspendibleThreadSet::synchronize() {
pliden@6906	75	assert(Thread::current()->is_VM_thread(), "Must be the VM thread");
pliden@6906	76	if (ConcGCYieldTimeout > 0) {
pliden@6906	77	_suspend_all_start = os::elapsedTime();
pliden@6906	78	}
pliden@6906	79	MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
pliden@6906	80	assert(!_suspend_all, "Only one at a time");
pliden@6906	81	_suspend_all = true;
pliden@6906	82	while (_nthreads_stopped < _nthreads) {
pliden@6906	83	ml.wait(Mutex::_no_safepoint_check_flag);
pliden@6906	84	}
pliden@6906	85	}
pliden@6906	86
pliden@6906	87	void SuspendibleThreadSet::desynchronize() {
pliden@6906	88	assert(Thread::current()->is_VM_thread(), "Must be the VM thread");
pliden@6906	89	MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
pliden@6906	90	assert(_nthreads_stopped == _nthreads, "Invalid");
pliden@6906	91	_suspend_all = false;
pliden@6906	92	ml.notify_all();
pliden@6906	93	}