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/* Copyright 2012, 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.
*/
#include <inttypes.h>
#include <stdio.h>
#include <time.h>
#include "csem.h"
#include "ipc_lock.h"
static int lock_init(struct ipc_lock *lock)
{
if (lock->sem < 0) {
/* get or create the semaphore, init to 1 if needed */
int sem = csem_get_or_create(lock->key, 1);
if (sem < 0)
return -1;
lock->sem = sem;
}
return 0;
}
static void msecs_to_timespec(int msecs, struct timespec *tmspec)
{
tmspec->tv_sec = msecs / 1000;
tmspec->tv_nsec = (msecs % 1000) * 1000 * 1000;
}
int acquire_lock(struct ipc_lock *lock, int timeout_msecs)
{
int ret;
struct timespec timeout;
struct timespec *timeout_ptr;
/* initialize the lock */
if (lock_init(lock) < 0) {
fprintf(stderr, "%s(): failed to init lock 0x%08x\n",
__func__, (uint32_t)lock->key);
return -1;
}
/* check if it is already held */
if (lock->is_held)
return 1;
/* calculate the timeout */
if (timeout_msecs >= 0) {
timeout_ptr = &timeout;
msecs_to_timespec(timeout_msecs, timeout_ptr);
} else {
timeout_ptr = NULL;
}
/* try to get the lock */
ret = csem_down_timeout_undo(lock->sem, timeout_ptr);
if (ret < 0) {
fprintf(stderr, "%s(): failed to acquire lock 0x%08x\n",
__func__, (uint32_t)lock->key);
return -1;
}
/* success */
lock->is_held = 1;
return 0;
}
int release_lock(struct ipc_lock *lock)
{
if (lock->is_held) {
lock->is_held = 0;
csem_up_undo(lock->sem);
/* NOTE: do not destroy the semaphore, we want it to persist */
return 0;
}
/* did not hold the lock */
return -1;
}