// Copyright (c) 2012 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 "rlz/lib/recursive_cross_process_lock_posix.h" #include #include #include #include #include #include #include "base/files/file_path.h" #include "base/logging.h" #include "base/posix/eintr_wrapper.h" namespace rlz_lib { bool RecursiveCrossProcessLock::TryGetCrossProcessLock( const base::FilePath& lock_filename) { bool just_got_lock = false; // Emulate a recursive mutex with a non-recursive one. if (pthread_mutex_trylock(&recursive_lock_) == EBUSY) { if (pthread_equal(pthread_self(), locking_thread_) == 0) { // Some other thread has the lock, wait for it. pthread_mutex_lock(&recursive_lock_); CHECK(locking_thread_ == 0); just_got_lock = true; } } else { just_got_lock = true; } locking_thread_ = pthread_self(); // Try to acquire file lock. if (just_got_lock) { const int kMaxTimeoutMS = 5000; // Matches Windows. const int kSleepPerTryMS = 200; CHECK(file_lock_ == -1); file_lock_ = open(lock_filename.value().c_str(), O_RDWR | O_CREAT, 0666); if (file_lock_ == -1) { perror("open"); return false; } int flock_result = -1; int elapsed_ms = 0; while ((flock_result = HANDLE_EINTR(flock(file_lock_, LOCK_EX | LOCK_NB))) == -1 && errno == EWOULDBLOCK && elapsed_ms < kMaxTimeoutMS) { usleep(kSleepPerTryMS * 1000); elapsed_ms += kSleepPerTryMS; } if (flock_result == -1) { perror("flock"); close(file_lock_); file_lock_ = -1; return false; } return true; } else { return file_lock_ != -1; } } void RecursiveCrossProcessLock::ReleaseLock() { if (file_lock_ != -1) { ignore_result(HANDLE_EINTR(flock(file_lock_, LOCK_UN))); close(file_lock_); file_lock_ = -1; } locking_thread_ = 0; pthread_mutex_unlock(&recursive_lock_); } } // namespace rlz_lib