74 lines
2.8 KiB
C++
74 lines
2.8 KiB
C++
/*
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* Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "memory/iterator.hpp"
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#include "runtime/atomic.hpp"
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#include "runtime/thread.hpp"
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#include "runtime/threadSMR.inline.hpp"
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#include "runtime/vmThread.hpp"
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#include "utilities/globalCounter.hpp"
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#include "utilities/spinYield.hpp"
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GlobalCounter::PaddedCounter GlobalCounter::_global_counter;
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class GlobalCounter::CounterThreadCheck : public ThreadClosure {
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private:
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uintx _gbl_cnt;
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public:
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CounterThreadCheck(uintx gbl_cnt) : _gbl_cnt(gbl_cnt) {}
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void do_thread(Thread* thread) {
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SpinYield yield;
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// Loops on this thread until it has exited the critical read section.
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while(true) {
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uintx cnt = Atomic::load_acquire(thread->get_rcu_counter());
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// This checks if the thread's counter is active. And if so is the counter
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// for a pre-existing reader (belongs to this grace period). A pre-existing
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// reader will have a lower counter than the global counter version for this
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// generation. If the counter is larger than the global counter version this
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// is a new reader and we can continue.
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if (((cnt & COUNTER_ACTIVE) != 0) && (cnt - _gbl_cnt) > (max_uintx / 2)) {
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yield.wait();
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} else {
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break;
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}
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}
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}
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};
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void GlobalCounter::write_synchronize() {
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assert((*Thread::current()->get_rcu_counter() & COUNTER_ACTIVE) == 0x0, "must be outside a critcal section");
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// Atomic::add must provide fence since we have storeload dependency.
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uintx gbl_cnt = Atomic::add(&_global_counter._counter, COUNTER_INCREMENT);
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// Do all RCU threads.
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CounterThreadCheck ctc(gbl_cnt);
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for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
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ctc.do_thread(thread);
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}
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for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
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ctc.do_thread(njti.current());
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}
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}
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