Remove rtc::GlobalLock.

This change migrates a last stray consumer of GlobalLock
(SrtpSession) and removes all traces of GlobalLock/GlobalLockScope
from WebRTC.

Bug: webrtc:11567
Change-Id: I28059f2a10075815a4bdee8c357b9d3b6e50f18b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/179361
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31736}

5 files changed, 7 insertions, 68 deletions

diff --git a/pc/srtp_session.cc b/pc/srtp_session.cc
index 5ded455ee5..3aa488003f 100644
--- a/pc/srtp_session.cc
+++ b/pc/srtp_session.cc
@@ -13,7 +13,6 @@
 #include "absl/base/attributes.h"
 #include "media/base/rtp_utils.h"
 #include "pc/external_hmac.h"
-#include "rtc_base/critical_section.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/ssl_stream_adapter.h"
 #include "system_wrappers/include/metrics.h"
@@ -364,16 +363,16 @@ bool SrtpSession::UpdateKey(int type,
 }
 
 ABSL_CONST_INIT int g_libsrtp_usage_count = 0;
-ABSL_CONST_INIT rtc::GlobalLock g_libsrtp_lock;
+ABSL_CONST_INIT webrtc::GlobalMutex g_libsrtp_lock(absl::kConstInit);
 
 void ProhibitLibsrtpInitialization() {
-  rtc::GlobalLockScope ls(&g_libsrtp_lock);
+  webrtc::GlobalMutexLock ls(&g_libsrtp_lock);
   ++g_libsrtp_usage_count;
 }
 
 // static
 bool SrtpSession::IncrementLibsrtpUsageCountAndMaybeInit() {
-  rtc::GlobalLockScope ls(&g_libsrtp_lock);
+  webrtc::GlobalMutexLock ls(&g_libsrtp_lock);
 
   RTC_DCHECK_GE(g_libsrtp_usage_count, 0);
   if (g_libsrtp_usage_count == 0) {
@@ -402,7 +401,7 @@ bool SrtpSession::IncrementLibsrtpUsageCountAndMaybeInit() {
 
 // static
 void SrtpSession::DecrementLibsrtpUsageCountAndMaybeDeinit() {
-  rtc::GlobalLockScope ls(&g_libsrtp_lock);
+  webrtc::GlobalMutexLock ls(&g_libsrtp_lock);
 
   RTC_DCHECK_GE(g_libsrtp_usage_count, 1);
   if (--g_libsrtp_usage_count == 0) {
diff --git a/pc/srtp_session.h b/pc/srtp_session.h
index e2f1b8d730..84445965b2 100644
--- a/pc/srtp_session.h
+++ b/pc/srtp_session.h
@@ -14,7 +14,8 @@
 #include <vector>
 
 #include "api/scoped_refptr.h"
-#include "rtc_base/critical_section.h"
+#include "rtc_base/constructor_magic.h"
+#include "rtc_base/synchronization/mutex.h"
 #include "rtc_base/thread_checker.h"
 
 // Forward declaration to avoid pulling in libsrtp headers here
@@ -124,7 +125,7 @@ class SrtpSession {
   int rtp_auth_tag_len_ = 0;
   int rtcp_auth_tag_len_ = 0;
   bool inited_ = false;
-  static rtc::GlobalLock lock_;
+  static webrtc::GlobalMutex lock_;
   int last_send_seq_num_ = -1;
   bool external_auth_active_ = false;
   bool external_auth_enabled_ = false;
diff --git a/rtc_base/critical_section.cc b/rtc_base/critical_section.cc
index c6b17ff1b2..1f68299aab 100644
--- a/rtc_base/critical_section.cc
+++ b/rtc_base/critical_section.cc
@@ -217,23 +217,4 @@ CritScope::~CritScope() {
   cs_->Leave();
 }
 
-void GlobalLock::Lock() {
-  while (AtomicOps::CompareAndSwap(&lock_acquired_, 0, 1)) {
-    webrtc::YieldCurrentThread();
-  }
-}
-
-void GlobalLock::Unlock() {
-  int old_value = AtomicOps::CompareAndSwap(&lock_acquired_, 1, 0);
-  RTC_DCHECK_EQ(1, old_value) << "Unlock called without calling Lock first";
-}
-
-GlobalLockScope::GlobalLockScope(GlobalLock* lock) : lock_(lock) {
-  lock_->Lock();
-}
-
-GlobalLockScope::~GlobalLockScope() {
-  lock_->Unlock();
-}
-
 }  // namespace rtc
diff --git a/rtc_base/critical_section.h b/rtc_base/critical_section.h
index cf10463bdf..af16861447 100644
--- a/rtc_base/critical_section.h
+++ b/rtc_base/critical_section.h
@@ -95,29 +95,6 @@ class RTC_SCOPED_LOCKABLE CritScope {
   RTC_DISALLOW_COPY_AND_ASSIGN(CritScope);
 };
 
-// A lock used to protect global variables. Do NOT use for other purposes.
-class RTC_LOCKABLE GlobalLock {
- public:
-  constexpr GlobalLock() : lock_acquired_(0) {}
-
-  void Lock() RTC_EXCLUSIVE_LOCK_FUNCTION();
-  void Unlock() RTC_UNLOCK_FUNCTION();
-
- private:
-  volatile int lock_acquired_;
-};
-
-// GlobalLockScope, for serializing execution through a scope.
-class RTC_SCOPED_LOCKABLE GlobalLockScope {
- public:
-  explicit GlobalLockScope(GlobalLock* lock) RTC_EXCLUSIVE_LOCK_FUNCTION(lock);
-  ~GlobalLockScope() RTC_UNLOCK_FUNCTION();
-
- private:
-  GlobalLock* const lock_;
-  RTC_DISALLOW_COPY_AND_ASSIGN(GlobalLockScope);
-};
-
 }  // namespace rtc
 
 #endif  // RTC_BASE_CRITICAL_SECTION_H_
diff --git a/rtc_base/critical_section_unittest.cc b/rtc_base/critical_section_unittest.cc
index 16aefd2740..52d0a8f865 100644
--- a/rtc_base/critical_section_unittest.cc
+++ b/rtc_base/critical_section_unittest.cc
@@ -282,25 +282,6 @@ TEST(AtomicOpsTest, CompareAndSwap) {
   EXPECT_EQ(1, runner.shared_value());
 }
 
-TEST(GlobalLockTest, CanHaveStaticStorageDuration) {
-  static_assert(std::is_trivially_destructible<GlobalLock>::value, "");
-  ABSL_CONST_INIT static GlobalLock global_lock;
-  global_lock.Lock();
-  global_lock.Unlock();
-}
-
-TEST(GlobalLockTest, Basic) {
-  // Create and start lots of threads.
-  LockRunner<GlobalLock> runner;
-  std::vector<std::unique_ptr<Thread>> threads;
-  StartThreads(&threads, &runner);
-  runner.SetExpectedThreadCount(kNumThreads);
-
-  // Release the hounds!
-  EXPECT_TRUE(runner.Run());
-  EXPECT_EQ(0, runner.shared_value());
-}
-
 TEST(CriticalSectionTest, Basic) {
   // Create and start lots of threads.
   LockRunner<CriticalSectionLock> runner;