[base] Use absl::Mutex for SharedMutex

LeszekSwirski · V8 LUCI CQ · commit dc0e30522358 · 2024-12-13T09:02:50.000-08:00
std::shared_mutex doesn't seem very performance optimized in libc++, and we see it spending a lot of time in the kernel even under low contention. Mac only for now, since this is the only platform where we use std::shared_mutex, but we should try unifying with other platforms too. Change-Id: I984692918dd611dd8595059345b31531f1fe3071 Bug: 383975879 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6088023 Commit-Queue: Michael Lippautz <mlippautz@chromium.org> Auto-Submit: Leszek Swirski <leszeks@chromium.org> Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Cr-Commit-Position: refs/heads/main@{#97768}
diff --git a/BUILD.gn b/BUILD.gn
@@ -6649,6 +6649,8 @@ v8_component("v8_libbase") {
 
   deps = [ ":v8_config_headers" ]
 
+  public_deps = [ ":v8_abseil" ]
+
   if (current_os == "zos") {
     public_configs += [ ":zoslib_config" ]
     deps += [ ":zoslib" ]
diff --git a/DEPS b/DEPS
@@ -526,6 +526,7 @@ include_rules = [
   '+absl/container/flat_hash_set.h',
   '+absl/container/btree_map.h',
   '+absl/status',
+  '+absl/synchronization/mutex.h',
   # Some abseil features are explicitly banned.
   '-absl/types/any.h', # Requires RTTI.
   '-absl/types/flags', # Requires RTTI.
diff --git a/src/base/platform/mutex.cc b/src/base/platform/mutex.cc
@@ -231,36 +231,38 @@ bool RecursiveMutex::TryLock() {
 SharedMutex::SharedMutex() = default;
 SharedMutex::~SharedMutex() = default;
 
-void SharedMutex::LockShared() {
+void SharedMutex::LockShared() ABSL_SHARED_LOCK_FUNCTION(native_handle_) {
   DCHECK(TryHoldSharedMutex(this));
-  native_handle_.lock_shared();
+  native_handle_.ReaderLock();
 }
 
-void SharedMutex::LockExclusive() {
+void SharedMutex::LockExclusive() ABSL_EXCLUSIVE_LOCK_FUNCTION(native_handle_) {
   DCHECK(TryHoldSharedMutex(this));
-  native_handle_.lock();
+  native_handle_.Lock();
 }
 
-void SharedMutex::UnlockShared() {
+void SharedMutex::UnlockShared() ABSL_UNLOCK_FUNCTION(native_handle_) {
   DCHECK(TryReleaseSharedMutex(this));
-  native_handle_.unlock_shared();
+  native_handle_.ReaderUnlock();
 }
 
-void SharedMutex::UnlockExclusive() {
+void SharedMutex::UnlockExclusive() ABSL_UNLOCK_FUNCTION(native_handle_) {
   DCHECK(TryReleaseSharedMutex(this));
-  native_handle_.unlock();
+  native_handle_.Unlock();
 }
 
-bool SharedMutex::TryLockShared() {
+bool SharedMutex::TryLockShared()
+    ABSL_SHARED_TRYLOCK_FUNCTION(true, native_handle_) {
   DCHECK(SharedMutexNotHeld(this));
-  bool result = native_handle_.try_lock_shared();
+  bool result = native_handle_.ReaderTryLock();
   if (result) DCHECK(TryHoldSharedMutex(this));
   return result;
 }
 
-bool SharedMutex::TryLockExclusive() {
+bool SharedMutex::TryLockExclusive()
+    ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true, native_handle_) {
   DCHECK(SharedMutexNotHeld(this));
-  bool result = native_handle_.try_lock();
+  bool result = native_handle_.TryLock();
   if (result) DCHECK(TryHoldSharedMutex(this));
   return result;
 }
diff --git a/src/base/platform/mutex.h b/src/base/platform/mutex.h
@@ -10,7 +10,7 @@
 #include "include/v8config.h"
 
 #if V8_OS_DARWIN
-#include <shared_mutex>
+#include "absl/synchronization/mutex.h"
 #endif
 
 #if V8_OS_POSIX
@@ -296,7 +296,7 @@ class V8_BASE_EXPORT SharedMutex final {
   // pthread_rwlock_t is broken on MacOS when signals are being sent to the
   // process (see https://crbug.com/v8/11399).
   // We thus use std::shared_mutex on MacOS, which does not have this problem.
-  using NativeHandle = std::shared_mutex;
+  using NativeHandle = absl::Mutex;
 #elif V8_OS_POSIX
   using NativeHandle = pthread_rwlock_t;
 #elif V8_OS_WIN
