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// 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 <errno.h>
#include <fcntl.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#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) {
VPLOG(1) << "Failed to open: " << lock_filename.value();
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) {
VPLOG(1) << "Failed flock: " << lock_filename.value();
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
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