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525 lines
17 KiB
C++
525 lines
17 KiB
C++
/*
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* Copyright (c) 1998, 2023, 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 "logging/log.hpp"
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#include "memory/resourceArea.hpp"
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#include "runtime/interfaceSupport.inline.hpp"
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#include "runtime/javaThread.inline.hpp"
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#include "runtime/mutex.hpp"
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#include "runtime/os.inline.hpp"
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#include "runtime/osThread.hpp"
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#include "runtime/safepointMechanism.inline.hpp"
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#include "runtime/threadCrashProtection.hpp"
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#include "utilities/events.hpp"
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#include "utilities/macros.hpp"
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class InFlightMutexRelease {
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private:
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Mutex* _in_flight_mutex;
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public:
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InFlightMutexRelease(Mutex* in_flight_mutex) : _in_flight_mutex(in_flight_mutex) {
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assert(in_flight_mutex != nullptr, "must be");
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}
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void operator()(JavaThread* current) {
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_in_flight_mutex->release_for_safepoint();
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_in_flight_mutex = nullptr;
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}
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bool not_released() { return _in_flight_mutex != nullptr; }
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};
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#ifdef ASSERT
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void Mutex::check_block_state(Thread* thread) {
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if (!_allow_vm_block && thread->is_VM_thread()) {
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// JavaThreads are checked to make sure that they do not hold _allow_vm_block locks during operations
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// that could safepoint. Make sure the vm thread never uses locks with _allow_vm_block == false.
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fatal("VM thread could block on lock that may be held by a JavaThread during safepoint: %s", name());
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}
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assert(!ThreadCrashProtection::is_crash_protected(thread),
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"locking not allowed when crash protection is set");
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}
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void Mutex::check_safepoint_state(Thread* thread) {
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check_block_state(thread);
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// If the lock acquisition checks for safepoint, verify that the lock was created with rank that
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// has safepoint checks. Technically this doesn't affect NonJavaThreads since they won't actually
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// check for safepoint, but let's make the rule unconditional unless there's a good reason not to.
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assert(_rank > nosafepoint,
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"This lock should not be taken with a safepoint check: %s", name());
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if (thread->is_active_Java_thread()) {
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// Also check NoSafepointVerifier, and thread state is _thread_in_vm
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JavaThread::cast(thread)->check_for_valid_safepoint_state();
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}
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}
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void Mutex::check_no_safepoint_state(Thread* thread) {
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check_block_state(thread);
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assert(!thread->is_active_Java_thread() || _rank <= nosafepoint,
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"This lock should always have a safepoint check for Java threads: %s",
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name());
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}
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#endif // ASSERT
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void Mutex::lock_contended(Thread* self) {
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DEBUG_ONLY(int retry_cnt = 0;)
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bool is_active_Java_thread = self->is_active_Java_thread();
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do {
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#ifdef ASSERT
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if (retry_cnt++ > 3) {
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log_trace(vmmutex)("JavaThread " INTPTR_FORMAT " on %d attempt trying to acquire vmmutex %s", p2i(self), retry_cnt, _name);
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}
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#endif // ASSERT
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// Is it a JavaThread participating in the safepoint protocol.
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if (is_active_Java_thread) {
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InFlightMutexRelease ifmr(this);
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assert(rank() > Mutex::nosafepoint, "Potential deadlock with nosafepoint or lesser rank mutex");
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{
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ThreadBlockInVMPreprocess<InFlightMutexRelease> tbivmdc(JavaThread::cast(self), ifmr);
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_lock.lock();
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}
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if (ifmr.not_released()) {
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// Not unlocked by ~ThreadBlockInVMPreprocess
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break;
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}
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} else {
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_lock.lock();
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break;
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}
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} while (!_lock.try_lock());
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}
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void Mutex::lock(Thread* self) {
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assert(owner() != self, "invariant");
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check_safepoint_state(self);
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check_rank(self);
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if (!_lock.try_lock()) {
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// The lock is contended, use contended slow-path function to lock
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lock_contended(self);
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}
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assert_owner(nullptr);
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set_owner(self);
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}
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void Mutex::lock() {
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lock(Thread::current());
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}
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// Lock without safepoint check - a degenerate variant of lock() for use by
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// JavaThreads when it is known to be safe to not check for a safepoint when
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// acquiring this lock. If the thread blocks acquiring the lock it is not
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// safepoint-safe and so will prevent a safepoint from being reached. If used
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// in the wrong way this can lead to a deadlock with the safepoint code.
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void Mutex::lock_without_safepoint_check(Thread * self) {
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assert(owner() != self, "invariant");
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check_no_safepoint_state(self);
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check_rank(self);
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_lock.lock();
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assert_owner(nullptr);
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set_owner(self);
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}
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void Mutex::lock_without_safepoint_check() {
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lock_without_safepoint_check(Thread::current());
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}
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// Returns true if thread succeeds in grabbing the lock, otherwise false.
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bool Mutex::try_lock_inner(bool do_rank_checks) {
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Thread * const self = Thread::current();
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// Checking the owner hides the potential difference in recursive locking behaviour
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// on some platforms.
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if (owner() == self) {
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return false;
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}
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if (do_rank_checks) {
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check_rank(self);
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}
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// Some safepoint checking locks use try_lock, so cannot check
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// safepoint state, but can check blocking state.
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check_block_state(self);
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if (_lock.try_lock()) {
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assert_owner(nullptr);
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set_owner(self);
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return true;
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}
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return false;
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}
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bool Mutex::try_lock() {
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return try_lock_inner(true /* do_rank_checks */);
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}
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bool Mutex::try_lock_without_rank_check() {
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bool res = try_lock_inner(false /* do_rank_checks */);
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DEBUG_ONLY(if (res) _skip_rank_check = true;)
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return res;
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}
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void Mutex::release_for_safepoint() {
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assert_owner(nullptr);
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_lock.unlock();
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}
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void Mutex::unlock() {
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DEBUG_ONLY(assert_owner(Thread::current()));
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set_owner(nullptr);
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_lock.unlock();
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}
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void Monitor::notify() {
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DEBUG_ONLY(assert_owner(Thread::current()));
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_lock.notify();
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}
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void Monitor::notify_all() {
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DEBUG_ONLY(assert_owner(Thread::current()));
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_lock.notify_all();
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}
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// timeout is in milliseconds - with zero meaning never timeout
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bool Monitor::wait_without_safepoint_check(uint64_t timeout) {
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Thread* const self = Thread::current();
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assert_owner(self);
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check_rank(self);
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// conceptually set the owner to null in anticipation of
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// abdicating the lock in wait
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set_owner(nullptr);
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// Check safepoint state after resetting owner and possible NSV.
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check_no_safepoint_state(self);
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int wait_status = _lock.wait(timeout);
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set_owner(self);
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return wait_status != 0; // return true IFF timeout
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}
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// timeout is in milliseconds - with zero meaning never timeout
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bool Monitor::wait(uint64_t timeout) {
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JavaThread* const self = JavaThread::current();
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// Safepoint checking logically implies an active JavaThread.
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assert(self->is_active_Java_thread(), "invariant");
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assert_owner(self);
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check_rank(self);
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// conceptually set the owner to null in anticipation of
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// abdicating the lock in wait
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set_owner(nullptr);
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// Check safepoint state after resetting owner and possible NSV.
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check_safepoint_state(self);
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int wait_status;
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InFlightMutexRelease ifmr(this);
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{
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ThreadBlockInVMPreprocess<InFlightMutexRelease> tbivmdc(self, ifmr);
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OSThreadWaitState osts(self->osthread(), false /* not Object.wait() */);
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wait_status = _lock.wait(timeout);
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}
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if (ifmr.not_released()) {
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// Not unlocked by ~ThreadBlockInVMPreprocess
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assert_owner(nullptr);
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// Conceptually reestablish ownership of the lock.
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set_owner(self);
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} else {
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lock(self);
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}
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return wait_status != 0; // return true IFF timeout
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}
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Mutex::~Mutex() {
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assert_owner(nullptr);
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os::free(const_cast<char*>(_name));
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}
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Mutex::Mutex(Rank rank, const char * name, bool allow_vm_block) : _owner(nullptr) {
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assert(os::mutex_init_done(), "Too early!");
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assert(name != nullptr, "Mutex requires a name");
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_name = os::strdup(name, mtInternal);
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#ifdef ASSERT
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_allow_vm_block = allow_vm_block;
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_rank = rank;
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_skip_rank_check = false;
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assert(_rank >= static_cast<Rank>(0) && _rank <= safepoint, "Bad lock rank %s: %s", rank_name(), name);
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// The allow_vm_block also includes allowing other non-Java threads to block or
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// allowing Java threads to block in native.
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assert(_rank > nosafepoint || _allow_vm_block,
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"Locks that don't check for safepoint should always allow the vm to block: %s", name);
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#endif
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}
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bool Mutex::owned_by_self() const {
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return owner() == Thread::current();
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}
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void Mutex::print_on_error(outputStream* st) const {
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st->print("[" PTR_FORMAT, p2i(this));
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st->print("] %s", _name);
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st->print(" - owner thread: " PTR_FORMAT, p2i(owner()));
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}
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// ----------------------------------------------------------------------------------
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// Non-product code
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//
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#ifdef ASSERT
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static Mutex::Rank _ranks[] = { Mutex::event, Mutex::service, Mutex::stackwatermark, Mutex::tty, Mutex::oopstorage,
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Mutex::nosafepoint, Mutex::safepoint };
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static const char* _rank_names[] = { "event", "service", "stackwatermark", "tty", "oopstorage",
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"nosafepoint", "safepoint" };
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static const int _num_ranks = 7;
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static const char* rank_name_internal(Mutex::Rank r) {
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// Find closest rank and print out the name
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stringStream st;
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for (int i = 0; i < _num_ranks; i++) {
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if (r == _ranks[i]) {
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return _rank_names[i];
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} else if (r > _ranks[i] && (i < _num_ranks-1 && r < _ranks[i+1])) {
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int delta = static_cast<int>(_ranks[i+1]) - static_cast<int>(r);
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st.print("%s-%d", _rank_names[i+1], delta);
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return st.as_string();
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}
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}
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return "fail";
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}
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const char* Mutex::rank_name() const {
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return rank_name_internal(_rank);
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}
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void Mutex::assert_no_overlap(Rank orig, Rank adjusted, int adjust) {
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int i = 0;
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while (_ranks[i] < orig) i++;
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// underflow is caught in constructor
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if (i != 0 && adjusted > event && adjusted <= _ranks[i-1]) {
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ResourceMark rm;
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assert(adjusted > _ranks[i-1],
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"Rank %s-%d overlaps with %s",
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rank_name_internal(orig), adjust, rank_name_internal(adjusted));
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}
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}
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#endif // ASSERT
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#ifndef PRODUCT
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void Mutex::print_on(outputStream* st) const {
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st->print("Mutex: [" PTR_FORMAT "] %s - owner: " PTR_FORMAT,
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p2i(this), _name, p2i(owner()));
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if (_allow_vm_block) {
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st->print("%s", " allow_vm_block");
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}
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DEBUG_ONLY(st->print(" %s", rank_name()));
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st->cr();
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}
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void Mutex::print() const {
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print_on(::tty);
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}
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#endif // PRODUCT
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#ifdef ASSERT
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void Mutex::assert_owner(Thread * expected) {
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const char* msg = "invalid owner";
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if (expected == nullptr) {
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msg = "should be un-owned";
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}
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else if (expected == Thread::current()) {
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msg = "should be owned by current thread";
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}
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assert(owner() == expected,
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"%s: owner=" INTPTR_FORMAT ", should be=" INTPTR_FORMAT,
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msg, p2i(owner()), p2i(expected));
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}
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Mutex* Mutex::get_least_ranked_lock(Mutex* locks) {
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Mutex *res, *tmp;
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for (res = tmp = locks; tmp != nullptr; tmp = tmp->next()) {
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if (tmp->rank() < res->rank()) {
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res = tmp;
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}
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}
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return res;
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}
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Mutex* Mutex::get_least_ranked_lock_besides_this(Mutex* locks) {
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Mutex *res, *tmp;
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for (res = nullptr, tmp = locks; tmp != nullptr; tmp = tmp->next()) {
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if (tmp != this && (res == nullptr || tmp->rank() < res->rank())) {
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res = tmp;
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}
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}
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assert(res != this, "invariant");
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return res;
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}
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// Tests for rank violations that might indicate exposure to deadlock.
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void Mutex::check_rank(Thread* thread) {
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Mutex* locks_owned = thread->owned_locks();
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// We expect the locks already acquired to be in increasing rank order,
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// modulo locks acquired in try_lock_without_rank_check()
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for (Mutex* tmp = locks_owned; tmp != nullptr; tmp = tmp->next()) {
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if (tmp->next() != nullptr) {
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assert(tmp->rank() < tmp->next()->rank()
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|| tmp->skip_rank_check(), "mutex rank anomaly?");
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}
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}
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if (owned_by_self()) {
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// wait() case
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Mutex* least = get_least_ranked_lock_besides_this(locks_owned);
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// For JavaThreads, we enforce not holding locks of rank nosafepoint or lower while waiting
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// because the held lock has a NoSafepointVerifier so waiting on a lower ranked lock will not be
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// able to check for safepoints first with a TBIVM.
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// For all threads, we enforce not holding the tty lock or below, since this could block progress also.
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// Also "this" should be the monitor with lowest rank owned by this thread.
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if (least != nullptr && ((least->rank() <= Mutex::nosafepoint && thread->is_Java_thread()) ||
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least->rank() <= Mutex::tty ||
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least->rank() <= this->rank())) {
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ResourceMark rm(thread);
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assert(false, "Attempting to wait on monitor %s/%s while holding lock %s/%s -- "
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"possible deadlock. %s", name(), rank_name(), least->name(), least->rank_name(),
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least->rank() <= this->rank() ?
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"Should wait on the least ranked monitor from all owned locks." :
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thread->is_Java_thread() ?
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"Should not block(wait) while holding a lock of rank nosafepoint or below." :
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"Should not block(wait) while holding a lock of rank tty or below.");
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}
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} else {
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// lock()/lock_without_safepoint_check()/try_lock() case
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Mutex* least = get_least_ranked_lock(locks_owned);
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// Deadlock prevention rules require us to acquire Mutexes only in
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// a global total order. For example, if m1 is the lowest ranked mutex
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// that the thread holds and m2 is the mutex the thread is trying
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// to acquire, then deadlock prevention rules require that the rank
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// of m2 be less than the rank of m1. This prevents circular waits.
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if (least != nullptr && least->rank() <= this->rank()) {
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ResourceMark rm(thread);
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if (least->rank() > Mutex::tty) {
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// Printing owned locks acquires tty lock. If the least rank was below or equal
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// tty, then deadlock detection code would circle back here, until we run
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// out of stack and crash hard. Print locks only when it is safe.
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thread->print_owned_locks();
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}
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assert(false, "Attempting to acquire lock %s/%s out of order with lock %s/%s -- "
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"possible deadlock", this->name(), this->rank_name(), least->name(), least->rank_name());
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}
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}
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}
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// Called immediately after lock acquisition or release as a diagnostic
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// to track the lock-set of the thread.
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// Rather like an EventListener for _owner (:>).
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void Mutex::set_owner_implementation(Thread *new_owner) {
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// This function is solely responsible for maintaining
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// and checking the invariant that threads and locks
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// are in a 1/N relation, with some some locks unowned.
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// It uses the Mutex::_owner, Mutex::_next, and
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// Thread::_owned_locks fields, and no other function
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// changes those fields.
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// It is illegal to set the mutex from one non-null
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// owner to another--it must be owned by null as an
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// intermediate state.
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if (new_owner != nullptr) {
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// the thread is acquiring this lock
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assert(new_owner == Thread::current(), "Should I be doing this?");
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assert(owner() == nullptr, "setting the owner thread of an already owned mutex");
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raw_set_owner(new_owner); // set the owner
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// link "this" into the owned locks list
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this->_next = new_owner->_owned_locks;
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new_owner->_owned_locks = this;
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// NSV implied with locking allow_vm_block flag.
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// The tty_lock is special because it is released for the safepoint by
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// the safepoint mechanism.
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if (new_owner->is_Java_thread() && _allow_vm_block && this != tty_lock) {
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JavaThread::cast(new_owner)->inc_no_safepoint_count();
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}
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} else {
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// the thread is releasing this lock
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Thread* old_owner = owner();
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_last_owner = old_owner;
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_skip_rank_check = false;
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assert(old_owner != nullptr, "removing the owner thread of an unowned mutex");
|
|
assert(old_owner == Thread::current(), "removing the owner thread of an unowned mutex");
|
|
|
|
raw_set_owner(nullptr); // set the owner
|
|
|
|
Mutex* locks = old_owner->owned_locks();
|
|
|
|
// remove "this" from the owned locks list
|
|
|
|
Mutex* prev = nullptr;
|
|
bool found = false;
|
|
for (; locks != nullptr; prev = locks, locks = locks->next()) {
|
|
if (locks == this) {
|
|
found = true;
|
|
break;
|
|
}
|
|
}
|
|
assert(found, "Removing a lock not owned");
|
|
if (prev == nullptr) {
|
|
old_owner->_owned_locks = _next;
|
|
} else {
|
|
prev->_next = _next;
|
|
}
|
|
_next = nullptr;
|
|
|
|
// ~NSV implied with locking allow_vm_block flag.
|
|
if (old_owner->is_Java_thread() && _allow_vm_block && this != tty_lock) {
|
|
JavaThread::cast(old_owner)->dec_no_safepoint_count();
|
|
}
|
|
}
|
|
}
|
|
#endif // ASSERT
|