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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
commit43a97878ce14b72f0981164f87f2e35e14151312 (patch)
tree620249daf56c0258faa40cbdcf9cfba06de2a846 /security/sandbox/chromium/base/synchronization/lock.h
parentInitial commit. (diff)
downloadfirefox-upstream.tar.xz
firefox-upstream.zip
Adding upstream version 110.0.1.upstream/110.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_SYNCHRONIZATION_LOCK_H_
+#define BASE_SYNCHRONIZATION_LOCK_H_
+
+#include "base/base_export.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/synchronization/lock_impl.h"
+#include "base/thread_annotations.h"
+#include "base/threading/platform_thread.h"
+#include "build/build_config.h"
+
+namespace base {
+
+// A convenient wrapper for an OS specific critical section. The only real
+// intelligence in this class is in debug mode for the support for the
+// AssertAcquired() method.
+class LOCKABLE BASE_EXPORT Lock {
+ public:
+#if !DCHECK_IS_ON()
+ // Optimized wrapper implementation
+ Lock() : lock_() {}
+ ~Lock() {}
+
+ // TODO(lukasza): https://crbug.com/831825: Add EXCLUSIVE_LOCK_FUNCTION
+ // annotation to Acquire method and similar annotations to Release and Try
+ // methods (here and in the #else branch).
+ void Acquire() { lock_.Lock(); }
+ void Release() { lock_.Unlock(); }
+
+ // If the lock is not held, take it and return true. If the lock is already
+ // held by another thread, immediately return false. This must not be called
+ // by a thread already holding the lock (what happens is undefined and an
+ // assertion may fail).
+ bool Try() { return lock_.Try(); }
+
+ // Null implementation if not debug.
+ void AssertAcquired() const ASSERT_EXCLUSIVE_LOCK() {}
+#else
+ Lock();
+ ~Lock();
+
+ // NOTE: We do not permit recursive locks and will commonly fire a DCHECK() if
+ // a thread attempts to acquire the lock a second time (while already holding
+ // it).
+ void Acquire() {
+ lock_.Lock();
+ CheckUnheldAndMark();
+ }
+ void Release() {
+ CheckHeldAndUnmark();
+ lock_.Unlock();
+ }
+
+ bool Try() {
+ bool rv = lock_.Try();
+ if (rv) {
+ CheckUnheldAndMark();
+ }
+ return rv;
+ }
+
+ void AssertAcquired() const ASSERT_EXCLUSIVE_LOCK();
+#endif // DCHECK_IS_ON()
+
+ // Whether Lock mitigates priority inversion when used from different thread
+ // priorities.
+ static bool HandlesMultipleThreadPriorities() {
+#if defined(OS_WIN)
+ // Windows mitigates priority inversion by randomly boosting the priority of
+ // ready threads.
+ // https://msdn.microsoft.com/library/windows/desktop/ms684831.aspx
+ return true;
+#elif defined(OS_POSIX) || defined(OS_FUCHSIA)
+ // POSIX mitigates priority inversion by setting the priority of a thread
+ // holding a Lock to the maximum priority of any other thread waiting on it.
+ return internal::LockImpl::PriorityInheritanceAvailable();
+#else
+#error Unsupported platform
+#endif
+ }
+
+ // Both Windows and POSIX implementations of ConditionVariable need to be
+ // able to see our lock and tweak our debugging counters, as they release and
+ // acquire locks inside of their condition variable APIs.
+ friend class ConditionVariable;
+
+ private:
+#if DCHECK_IS_ON()
+ // Members and routines taking care of locks assertions.
+ // Note that this checks for recursive locks and allows them
+ // if the variable is set. This is allowed by the underlying implementation
+ // on windows but not on Posix, so we're doing unneeded checks on Posix.
+ // It's worth it to share the code.
+ void CheckHeldAndUnmark();
+ void CheckUnheldAndMark();
+
+ // All private data is implicitly protected by lock_.
+ // Be VERY careful to only access members under that lock.
+ base::PlatformThreadRef owning_thread_ref_;
+#endif // DCHECK_IS_ON()
+
+ // Platform specific underlying lock implementation.
+ internal::LockImpl lock_;
+
+ DISALLOW_COPY_AND_ASSIGN(Lock);
+};
+
+// A helper class that acquires the given Lock while the AutoLock is in scope.
+using AutoLock = internal::BasicAutoLock<Lock>;
+
+// AutoUnlock is a helper that will Release() the |lock| argument in the
+// constructor, and re-Acquire() it in the destructor.
+using AutoUnlock = internal::BasicAutoUnlock<Lock>;
+
+// Like AutoLock but is a no-op when the provided Lock* is null. Inspired from
+// absl::MutexLockMaybe. Use this instead of base::Optional<base::AutoLock> to
+// get around -Wthread-safety-analysis warnings for conditional locking.
+using AutoLockMaybe = internal::BasicAutoLockMaybe<Lock>;
+
+// Like AutoLock but permits Release() of its mutex before destruction.
+// Release() may be called at most once. Inspired from
+// absl::ReleasableMutexLock. Use this instead of base::Optional<base::AutoLock>
+// to get around -Wthread-safety-analysis warnings for AutoLocks that are
+// explicitly released early (prefer proper scoping to this).
+using ReleasableAutoLock = internal::BasicReleasableAutoLock<Lock>;
+
+} // namespace base
+
+#endif // BASE_SYNCHRONIZATION_LOCK_H_