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