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 <errno.h> 8 #include <fcntl.h> 9 #include <sys/file.h> 10 #include <sys/stat.h> 11 #include <sys/types.h> 12 #include <unistd.h> 13 14 #include "base/files/file_path.h" 15 #include "base/logging.h" 16 #include "base/posix/eintr_wrapper.h" 17 18 namespace rlz_lib { 19 TryGetCrossProcessLock(const base::FilePath & lock_filename)20bool RecursiveCrossProcessLock::TryGetCrossProcessLock( 21 const base::FilePath& lock_filename) { 22 bool just_got_lock = false; 23 24 // Emulate a recursive mutex with a non-recursive one. 25 if (pthread_mutex_trylock(&recursive_lock_) == EBUSY) { 26 if (pthread_equal(pthread_self(), locking_thread_) == 0) { 27 // Some other thread has the lock, wait for it. 28 pthread_mutex_lock(&recursive_lock_); 29 CHECK(locking_thread_ == 0); 30 just_got_lock = true; 31 } 32 } else { 33 just_got_lock = true; 34 } 35 36 locking_thread_ = pthread_self(); 37 38 // Try to acquire file lock. 39 if (just_got_lock) { 40 const int kMaxTimeoutMS = 5000; // Matches Windows. 41 const int kSleepPerTryMS = 200; 42 43 CHECK(file_lock_ == -1); 44 file_lock_ = open(lock_filename.value().c_str(), O_RDWR | O_CREAT, 0666); 45 if (file_lock_ == -1) { 46 perror("open"); 47 return false; 48 } 49 50 int flock_result = -1; 51 int elapsed_ms = 0; 52 while ((flock_result = 53 HANDLE_EINTR(flock(file_lock_, LOCK_EX | LOCK_NB))) == -1 && 54 errno == EWOULDBLOCK && 55 elapsed_ms < kMaxTimeoutMS) { 56 usleep(kSleepPerTryMS * 1000); 57 elapsed_ms += kSleepPerTryMS; 58 } 59 60 if (flock_result == -1) { 61 perror("flock"); 62 close(file_lock_); 63 file_lock_ = -1; 64 return false; 65 } 66 return true; 67 } else { 68 return file_lock_ != -1; 69 } 70 } 71 ReleaseLock()72void RecursiveCrossProcessLock::ReleaseLock() { 73 if (file_lock_ != -1) { 74 ignore_result(HANDLE_EINTR(flock(file_lock_, LOCK_UN))); 75 close(file_lock_); 76 file_lock_ = -1; 77 } 78 79 locking_thread_ = 0; 80 pthread_mutex_unlock(&recursive_lock_); 81 } 82 83 } // namespace rlz_lib 84