Create a reader-writer lock implementaiton in base.

base/synchronization/rw_lock_posix.cc

+// Copyright 2016 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.
+
+#include "base/synchronization/rw_lock.h"
+
+#include "base/logging.h"
+
+namespace base {
+
+RWLock::RWLock() {

[danakj, 2016/05/19 23:01:37]

can you use PTHREAD_RWLOCK_INITIALIZER similar to windows?

[Anand Mistry (off Chromium), 2016/05/20 04:06:38]

Done.

Oddly enough, the man on Linux doesn't say this exists, but it is in SUSv2.

+  int rv = pthread_rwlock_init(&native_handle_, nullptr);

[danakj, 2016/05/19 23:01:37]

nit: name "result" instead of rv. ditto elsewhere

[Anand Mistry (off Chromium), 2016/05/20 04:06:38]

Done.

+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+RWLock::~RWLock() {
+  int rv = pthread_rwlock_destroy(&native_handle_);
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+void RWLock::ReadAcquire() {
+  int rv = pthread_rwlock_rdlock(&native_handle_);
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+void RWLock::ReadRelease() {
+  int rv = pthread_rwlock_unlock(&native_handle_);
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+void RWLock::WriteAcquire() {
+  int rv = pthread_rwlock_wrlock(&native_handle_);
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+void RWLock::WriteRelease() {
+  int rv = pthread_rwlock_unlock(&native_handle_);
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+}
+
+}  // namespace base