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Diffstat (limited to 'util/lock/file_lock.c')
| -rw-r--r-- | util/lock/file_lock.c | 262 |
1 files changed, 0 insertions, 262 deletions
diff --git a/util/lock/file_lock.c b/util/lock/file_lock.c deleted file mode 100644 index 36b420d287..0000000000 --- a/util/lock/file_lock.c +++ /dev/null @@ -1,262 +0,0 @@ -/* Copyright 2016, Google Inc. - * All rights reserved. - * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions are - * met: - * - * * Redistributions of source code must retain the above copyright - * notice, this list of conditions and the following disclaimer. - * * Redistributions in binary form must reproduce the above - * copyright notice, this list of conditions and the following - * disclaimer in the documentation and/or other materials provided - * with the distribution. - * * Neither the name of Google Inc. nor the names of its - * contributors may be used to endorse or promote products derived - * from this software without specific prior written permission. - * - * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS - * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT - * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR - * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT - * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, - * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT - * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, - * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY - * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT - * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE - * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. - * - * Alternatively, this software may be distributed under the terms of the - * GNU General Public License ("GPL") version 2 as published by the Free - * Software Foundation. - * - * file_lock.c: Implementation for a binary semaphore using a file lock. - * - * Warning: This relies on flock() which is known to be broken on NFS. - * - * The file will remain persistent once the lock has been used. Unfortunately, - * unlinking the file can introduce a race condition so we leave the file - * in place. - * - * The current process's PID will be written to the file for debug purposes. - */ - -#include <errno.h> -#include <fcntl.h> -#include <inttypes.h> -#include <limits.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include <time.h> -#include <unistd.h> -#include <sys/file.h> -#include <sys/types.h> -#include <sys/stat.h> - -#include "android.h" -#include "ipc_lock.h" -#include "locks.h" - -#define SLEEP_INTERVAL_MS 50 - -static void msecs_to_timespec(int msecs, struct timespec *tmspec) -{ - tmspec->tv_sec = msecs / 1000; - tmspec->tv_nsec = (msecs % 1000) * 1000 * 1000; -} - -static int lock_is_held(struct ipc_lock *lock) -{ - return lock->is_held; -} - -static int test_dir(const char *path) -{ - struct stat s; - - if (lstat(path, &s) < 0) { - fprintf(stderr, "Cannot stat %s.\n", path); - return -1; - } - - if (!S_ISDIR(s.st_mode)) { - fprintf(stderr, "%s is not a directory.\n", path); - return -1; - } - - return 0; -} - -static int file_lock_open_or_create(struct ipc_lock *lock) -{ - char path[PATH_MAX]; - - if (in_android()) { - char *tmpdir; - - tmpdir = android_tmpdir_path(); - if (!tmpdir) - return -1; - - if (snprintf(path, sizeof(path), "%s/%s", - tmpdir, lock->filename) < 0) { - return -1; - } - } else { - const char *dir = SYSTEM_LOCKFILE_DIR; - const char fallback[] = "/tmp"; - - if (test_dir(dir)) { - dir = fallback; - fprintf(stderr, "Trying fallback directory: %s\n", dir); - if (test_dir(dir)) - return -1; - } - - if (snprintf(path, sizeof(path), - "%s/%s", dir, lock->filename) < 0) - return -1; - - } - - lock->fd = open(path, O_RDWR | O_CREAT, 0600); - if (lock->fd < 0) { - fprintf(stderr, "Cannot open lockfile %s", path); - return -1; - } - - return 0; -} - -static int file_lock_get(struct ipc_lock *lock, int timeout_msecs) -{ - int msecs_remaining = timeout_msecs; - struct timespec sleep_interval, rem; - int ret = -1; - - if (timeout_msecs == 0) - return flock(lock->fd, LOCK_EX | LOCK_NB); - - msecs_to_timespec(SLEEP_INTERVAL_MS, &sleep_interval); - - while ((ret = flock(lock->fd, LOCK_EX | LOCK_NB)) != 0) { - if (errno != EWOULDBLOCK) { - fprintf(stderr, "Error obtaining lock"); - return -1; - } - - if (msecs_remaining < SLEEP_INTERVAL_MS) - msecs_to_timespec(msecs_remaining, &sleep_interval); - - while (nanosleep(&sleep_interval, &rem) != 0) { - if (errno == EINTR) { - sleep_interval = rem; - continue; - } else { - fprintf(stderr, "nanosleep() failed"); - return ret; - } - } - - if (timeout_msecs < 0) - continue; - - msecs_remaining -= SLEEP_INTERVAL_MS; - if (msecs_remaining < 0) - break; - } - - if (ret != 0) { - fprintf(stderr, "Timed out waiting for file lock.\n"); - return -1; - } - - return 0; -} - -static int file_lock_write_pid(struct ipc_lock *lock) -{ - ssize_t len; - /* - * PIDs are usually 5 digits, but we'll reserve enough room for - * a value of 2^32 (10 digits) out of paranoia. - */ - char pid_str[11]; - - if (ftruncate(lock->fd, 0) < 0) { - fprintf(stderr, "Cannot truncate lockfile"); - return -1; - } - - snprintf(pid_str, sizeof(pid_str), "%lu", (unsigned long)getpid()); - len = write(lock->fd, pid_str, strlen(pid_str)); - if (len < 0) { - fprintf(stderr, "Cannot write PID to lockfile"); - return -1; - } - - return 0; -} - -static void file_lock_release(struct ipc_lock *lock) -{ - if (flock(lock->fd, LOCK_UN) < 0) - fprintf(stderr, "Cannot release lock"); - - if (close(lock->fd) < 0) - fprintf(stderr, "Cannot close lockfile"); -} - -/* - * timeout <0 = no timeout (try forever) - * timeout 0 = do not wait (return immediately) - * timeout >0 = wait up to $timeout milliseconds - * - * returns 0 to indicate lock acquired - * returns >0 to indicate lock was already held - * returns <0 to indicate failed to acquire lock - */ -int acquire_lock(struct ipc_lock *lock, int timeout_msecs) -{ - /* check if it is already held */ - if (lock_is_held(lock)) - return 1; - - if (file_lock_open_or_create(lock)) - return -1; - - if (file_lock_get(lock, timeout_msecs)) { - lock->is_held = 0; - close(lock->fd); - return -1; - } else { - lock->is_held = 1; - } - - /* - * Write PID to lockfile for debug purposes. Failure to write to - * the file should not be considered fatal. There might be something - * bad happening with the filesystem, but the lock has already been - * obtained and we may need our tools for diagnostics and repairs - * so we should continue anyway. - */ - file_lock_write_pid(lock); - return 0; -} - -/* - * returns 0 if lock was released successfully - * returns -1 if lock had not been held before the call - */ -int release_lock(struct ipc_lock *lock) -{ - if (lock_is_held(lock)) { - file_lock_release(lock); - lock->is_held = 0; - return 0; - } - - return -1; -} |