Revert "Delete unused class GlobalMutex"
This reverts commit 5831afb8328cbecdbdbee882280ef907a09d9f31.
Reason for revert: The code is still in use: https://ci.chromium.org/ui/p/webrtc/builders/ci/Win32%20Builder%20(Clang)/10243/overview. It wasn't detected for some reasons.
Original change's description:
> Delete unused class GlobalMutex
>
> Bug: webrtc:13869
> Change-Id: Id3655bdd24630b78e83b606291605a37129fd4bc
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258131
> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#36478}
Bug: webrtc:13869
Change-Id: Id44dd4f8ec31ac9e05fc0ee75b55916e627fd7bf
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258135
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Artem Titov <titovartem@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36480}
diff --git a/rtc_base/synchronization/BUILD.gn b/rtc_base/synchronization/BUILD.gn
index 52c39d7..9d891f3 100644
--- a/rtc_base/synchronization/BUILD.gn
+++ b/rtc_base/synchronization/BUILD.gn
@@ -23,6 +23,7 @@
rtc_library("mutex") {
sources = [
+ "mutex.cc",
"mutex.h",
"mutex_critical_section.h",
"mutex_pthread.h",
diff --git a/rtc_base/synchronization/mutex.cc b/rtc_base/synchronization/mutex.cc
new file mode 100644
index 0000000..6c2d6ff
--- /dev/null
+++ b/rtc_base/synchronization/mutex.cc
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2020 The WebRTC Project Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "rtc_base/synchronization/mutex.h"
+
+#include "rtc_base/checks.h"
+#include "rtc_base/synchronization/yield.h"
+
+namespace webrtc {
+
+#if !defined(WEBRTC_ABSL_MUTEX)
+void GlobalMutex::Lock() {
+ while (mutex_locked_.exchange(1)) {
+ YieldCurrentThread();
+ }
+}
+
+void GlobalMutex::Unlock() {
+ int old = mutex_locked_.exchange(0);
+ RTC_DCHECK_EQ(old, 1) << "Unlock called without calling Lock first";
+}
+
+GlobalMutexLock::GlobalMutexLock(GlobalMutex* mutex) : mutex_(mutex) {
+ mutex_->Lock();
+}
+
+GlobalMutexLock::~GlobalMutexLock() {
+ mutex_->Unlock();
+}
+#endif // #if !defined(WEBRTC_ABSL_MUTEX)
+
+} // namespace webrtc
diff --git a/rtc_base/synchronization/mutex.h b/rtc_base/synchronization/mutex.h
index 2cf0e67..c6af9e9 100644
--- a/rtc_base/synchronization/mutex.h
+++ b/rtc_base/synchronization/mutex.h
@@ -72,6 +72,41 @@
Mutex* mutex_;
};
+// A mutex used to protect global variables. Do NOT use for other purposes.
+#if defined(WEBRTC_ABSL_MUTEX)
+using GlobalMutex = absl::Mutex;
+using GlobalMutexLock = absl::MutexLock;
+#else
+class RTC_LOCKABLE GlobalMutex final {
+ public:
+ GlobalMutex(const GlobalMutex&) = delete;
+ GlobalMutex& operator=(const GlobalMutex&) = delete;
+
+ constexpr explicit GlobalMutex(absl::ConstInitType /*unused*/)
+ : mutex_locked_(0) {}
+
+ void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION();
+ void Unlock() RTC_UNLOCK_FUNCTION();
+
+ private:
+ std::atomic<int> mutex_locked_; // 0 means lock not taken, 1 means taken.
+};
+
+// GlobalMutexLock, for serializing execution through a scope.
+class RTC_SCOPED_LOCKABLE GlobalMutexLock final {
+ public:
+ GlobalMutexLock(const GlobalMutexLock&) = delete;
+ GlobalMutexLock& operator=(const GlobalMutexLock&) = delete;
+
+ explicit GlobalMutexLock(GlobalMutex* mutex)
+ RTC_EXCLUSIVE_LOCK_FUNCTION(mutex_);
+ ~GlobalMutexLock() RTC_UNLOCK_FUNCTION();
+
+ private:
+ GlobalMutex* mutex_;
+};
+#endif // if defined(WEBRTC_ABSL_MUTEX)
+
} // namespace webrtc
#endif // RTC_BASE_SYNCHRONIZATION_MUTEX_H_
diff --git a/rtc_base/synchronization/mutex_unittest.cc b/rtc_base/synchronization/mutex_unittest.cc
index fcca78d..a07e8fa 100644
--- a/rtc_base/synchronization/mutex_unittest.cc
+++ b/rtc_base/synchronization/mutex_unittest.cc
@@ -177,5 +177,30 @@
EXPECT_EQ(0, runner.shared_value());
}
+TEST(MutexTest, ProtectsSharedResourceWithGlobalMutexAndRawMutexLocker) {
+ std::vector<std::unique_ptr<Thread>> threads;
+ LockRunner<GlobalMutex, RawMutexLocker<GlobalMutex>> runner(absl::kConstInit);
+ StartThreads(threads, &runner);
+ runner.SetExpectedThreadCount(kNumThreads);
+ EXPECT_TRUE(runner.Run());
+ EXPECT_EQ(0, runner.shared_value());
+}
+
+TEST(MutexTest, ProtectsSharedResourceWithGlobalMutexAndMutexLocker) {
+ std::vector<std::unique_ptr<Thread>> threads;
+ LockRunner<GlobalMutex, MutexLockLocker<GlobalMutex, GlobalMutexLock>> runner(
+ absl::kConstInit);
+ StartThreads(threads, &runner);
+ runner.SetExpectedThreadCount(kNumThreads);
+ EXPECT_TRUE(runner.Run());
+ EXPECT_EQ(0, runner.shared_value());
+}
+
+TEST(MutexTest, GlobalMutexCanHaveStaticStorageDuration) {
+ ABSL_CONST_INIT static GlobalMutex global_lock(absl::kConstInit);
+ global_lock.Lock();
+ global_lock.Unlock();
+}
+
} // namespace
} // namespace webrtc
