--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/suspendibleThreadSet.cpp Wed Oct 18 21:17:46 2017 +0200
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2014, 2017, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/shared/suspendibleThreadSet.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "runtime/semaphore.hpp"
+#include "runtime/thread.inline.hpp"
+
+uint SuspendibleThreadSet::_nthreads = 0;
+uint SuspendibleThreadSet::_nthreads_stopped = 0;
+bool SuspendibleThreadSet::_suspend_all = false;
+double SuspendibleThreadSet::_suspend_all_start = 0.0;
+
+static Semaphore* _synchronize_wakeup = NULL;
+
+void SuspendibleThreadSet_init() {
+ assert(_synchronize_wakeup == NULL, "STS already initialized");
+ _synchronize_wakeup = new Semaphore();
+}
+
+bool SuspendibleThreadSet::is_synchronized() {
+ assert_lock_strong(STS_lock);
+ assert(_nthreads_stopped <= _nthreads, "invariant");
+ return _nthreads_stopped == _nthreads;
+}
+
+void SuspendibleThreadSet::join() {
+ assert(!Thread::current()->is_suspendible_thread(), "Thread already joined");
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ while (_suspend_all) {
+ ml.wait(Mutex::_no_safepoint_check_flag);
+ }
+ _nthreads++;
+ DEBUG_ONLY(Thread::current()->set_suspendible_thread();)
+}
+
+void SuspendibleThreadSet::leave() {
+ assert(Thread::current()->is_suspendible_thread(), "Thread not joined");
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ assert(_nthreads > 0, "Invalid");
+ DEBUG_ONLY(Thread::current()->clear_suspendible_thread();)
+ _nthreads--;
+ if (_suspend_all && is_synchronized()) {
+ // This leave completes a request, so inform the requestor.
+ _synchronize_wakeup->signal();
+ }
+}
+
+void SuspendibleThreadSet::yield() {
+ assert(Thread::current()->is_suspendible_thread(), "Must have joined");
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ if (_suspend_all) {
+ _nthreads_stopped++;
+ if (is_synchronized()) {
+ if (ConcGCYieldTimeout > 0) {
+ double now = os::elapsedTime();
+ guarantee((now - _suspend_all_start) * 1000.0 < (double)ConcGCYieldTimeout, "Long delay");
+ }
+ // This yield completes the request, so inform the requestor.
+ _synchronize_wakeup->signal();
+ }
+ while (_suspend_all) {
+ ml.wait(Mutex::_no_safepoint_check_flag);
+ }
+ assert(_nthreads_stopped > 0, "Invalid");
+ _nthreads_stopped--;
+ }
+}
+
+void SuspendibleThreadSet::synchronize() {
+ assert(Thread::current()->is_VM_thread(), "Must be the VM thread");
+ if (ConcGCYieldTimeout > 0) {
+ _suspend_all_start = os::elapsedTime();
+ }
+ {
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ assert(!_suspend_all, "Only one at a time");
+ _suspend_all = true;
+ if (is_synchronized()) {
+ return;
+ }
+ } // Release lock before semaphore wait.
+
+ // Semaphore initial count is zero. To reach here, there must be at
+ // least one not yielded thread in the set, e.g. is_synchronized()
+ // was false before the lock was released. A thread in the set will
+ // signal the semaphore iff it is the last to yield or leave while
+ // there is an active suspend request. So there will be exactly one
+ // signal, which will increment the semaphore count to one, which
+ // will then be consumed by this wait, returning it to zero. No
+ // thread can exit yield or enter the set until desynchronize is
+ // called, so there are no further opportunities for the semaphore
+ // being signaled until we get back here again for some later
+ // synchronize call. Hence, there is no need to re-check for
+ // is_synchronized after the wait; it will always be true there.
+ _synchronize_wakeup->wait();
+
+#ifdef ASSERT
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ assert(_suspend_all, "STS not synchronizing");
+ assert(is_synchronized(), "STS not synchronized");
+#endif
+}
+
+void SuspendibleThreadSet::desynchronize() {
+ assert(Thread::current()->is_VM_thread(), "Must be the VM thread");
+ MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);
+ assert(_suspend_all, "STS not synchronizing");
+ assert(is_synchronized(), "STS not synchronized");
+ _suspend_all = false;
+ ml.notify_all();
+}