1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "rlz/lib/recursive_cross_process_lock_posix.h" 6 7 #include <fcntl.h> 8 #include <sys/file.h> 9 #include <sys/stat.h> 10 #include <sys/types.h> 11 #include <unistd.h> 12 13 #include "base/files/file_path.h" 14 #include "base/logging.h" 15 #include "base/posix/eintr_wrapper.h" 16 17 namespace rlz_lib { 18 19 bool RecursiveCrossProcessLock::TryGetCrossProcessLock( 20 const base::FilePath& lock_filename) { 21 bool just_got_lock = false; 22 23 // Emulate a recursive mutex with a non-recursive one. 24 if (pthread_mutex_trylock(&recursive_lock_) == EBUSY) { 25 if (pthread_equal(pthread_self(), locking_thread_) == 0) { 26 // Some other thread has the lock, wait for it. 27 pthread_mutex_lock(&recursive_lock_); 28 CHECK(locking_thread_ == 0); 29 just_got_lock = true; 30 } 31 } else { 32 just_got_lock = true; 33 } 34 35 locking_thread_ = pthread_self(); 36 37 // Try to acquire file lock. 38 if (just_got_lock) { 39 const int kMaxTimeoutMS = 5000; // Matches Windows. 40 const int kSleepPerTryMS = 200; 41 42 CHECK(file_lock_ == -1); 43 file_lock_ = open(lock_filename.value().c_str(), O_RDWR | O_CREAT, 0666); 44 if (file_lock_ == -1) { 45 perror("open"); 46 return false; 47 } 48 49 int flock_result = -1; 50 int elapsed_ms = 0; 51 while ((flock_result = 52 HANDLE_EINTR(flock(file_lock_, LOCK_EX | LOCK_NB))) == -1 && 53 errno == EWOULDBLOCK && 54 elapsed_ms < kMaxTimeoutMS) { 55 usleep(kSleepPerTryMS * 1000); 56 elapsed_ms += kSleepPerTryMS; 57 } 58 59 if (flock_result == -1) { 60 perror("flock"); 61 ignore_result(HANDLE_EINTR(close(file_lock_))); 62 file_lock_ = -1; 63 return false; 64 } 65 return true; 66 } else { 67 return file_lock_ != -1; 68 } 69 } 70 71 void RecursiveCrossProcessLock::ReleaseLock() { 72 if (file_lock_ != -1) { 73 ignore_result(HANDLE_EINTR(flock(file_lock_, LOCK_UN))); 74 ignore_result(HANDLE_EINTR(close(file_lock_))); 75 file_lock_ = -1; 76 } 77 78 locking_thread_ = 0; 79 pthread_mutex_unlock(&recursive_lock_); 80 } 81 82 } // namespace rlz_lib 83