1 /* 2 * Copyright (c) 2017 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include "modules/desktop_capture/screen_drawer_lock_posix.h" 12 13 #include <fcntl.h> 14 #include <sys/stat.h> 15 16 #include "absl/strings/string_view.h" 17 #include "rtc_base/checks.h" 18 #include "rtc_base/logging.h" 19 20 namespace webrtc { 21 22 namespace { 23 24 // A uuid as the name of semaphore. 25 static constexpr char kSemaphoreName[] = "GSDL54fe5552804711e6a7253f429a"; 26 27 } // namespace 28 ScreenDrawerLockPosix()29ScreenDrawerLockPosix::ScreenDrawerLockPosix() 30 : ScreenDrawerLockPosix(kSemaphoreName) {} 31 ScreenDrawerLockPosix(const char * name)32ScreenDrawerLockPosix::ScreenDrawerLockPosix(const char* name) { 33 semaphore_ = sem_open(name, O_CREAT, S_IRWXU | S_IRWXG | S_IRWXO, 1); 34 if (semaphore_ == SEM_FAILED) { 35 RTC_LOG_ERRNO(LS_ERROR) << "Failed to create named semaphore with " << name; 36 RTC_DCHECK_NOTREACHED(); 37 } 38 39 sem_wait(semaphore_); 40 } 41 ~ScreenDrawerLockPosix()42ScreenDrawerLockPosix::~ScreenDrawerLockPosix() { 43 if (semaphore_ == SEM_FAILED) { 44 return; 45 } 46 47 sem_post(semaphore_); 48 sem_close(semaphore_); 49 // sem_unlink a named semaphore won't wait until other clients to release the 50 // sem_t. So if a new process starts, it will sem_open a different kernel 51 // object with the same name and eventually breaks the cross-process lock. 52 } 53 54 // static Unlink(absl::string_view name)55void ScreenDrawerLockPosix::Unlink(absl::string_view name) { 56 sem_unlink(std::string(name).c_str()); 57 } 58 59 } // namespace webrtc 60