1 files changed, 59 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/desktop_capture/screen_drawer_lock_posix.cc b/third_party/libwebrtc/modules/desktop_capture/screen_drawer_lock_posix.cc
new file mode 100644
index 0000000000..28cb501fe7
--- /dev/null
+++ b/third_party/libwebrtc/modules/desktop_capture/screen_drawer_lock_posix.cc
@@ -0,0 +1,59 @@
+/*
+ *  Copyright (c) 2017 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 "modules/desktop_capture/screen_drawer_lock_posix.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include "absl/strings/string_view.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+namespace {
+
+// A uuid as the name of semaphore.
+static constexpr char kSemaphoreName[] = "GSDL54fe5552804711e6a7253f429a";
+
+}  // namespace
+
+ScreenDrawerLockPosix::ScreenDrawerLockPosix()
+    : ScreenDrawerLockPosix(kSemaphoreName) {}
+
+ScreenDrawerLockPosix::ScreenDrawerLockPosix(const char* name) {
+  semaphore_ = sem_open(name, O_CREAT, S_IRWXU | S_IRWXG | S_IRWXO, 1);
+  if (semaphore_ == SEM_FAILED) {
+    RTC_LOG_ERRNO(LS_ERROR) << "Failed to create named semaphore with " << name;
+    RTC_DCHECK_NOTREACHED();
+  }
+
+  sem_wait(semaphore_);
+}
+
+ScreenDrawerLockPosix::~ScreenDrawerLockPosix() {
+  if (semaphore_ == SEM_FAILED) {
+    return;
+  }
+
+  sem_post(semaphore_);
+  sem_close(semaphore_);
+  // sem_unlink a named semaphore won't wait until other clients to release the
+  // sem_t. So if a new process starts, it will sem_open a different kernel
+  // object with the same name and eventually breaks the cross-process lock.
+}
+
+// static
+void ScreenDrawerLockPosix::Unlink(absl::string_view name) {
+  sem_unlink(std::string(name).c_str());
+}
+
+}  // namespace webrtc