/**************************************************************************** * sched/pthread/pthread_mutexunlock.c * * Copyright (C) 2007-2009 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * 3. Neither the name NuttX 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. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include "pthread/pthread.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /**************************************************************************** * Private Type Declarations ****************************************************************************/ /**************************************************************************** * Global Variables ****************************************************************************/ /**************************************************************************** * Private Variables ****************************************************************************/ /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: pthread_mutex_unlock * * Description: * The pthread_mutex_unlock() function releases the mutex object referenced * by mutex. The manner in which a mutex is released is dependent upon the * mutex's type attribute. If there are threads blocked on the mutex object * referenced by mutex when pthread_mutex_unlock() is called, resulting in * the mutex becoming available, the scheduling policy is used to determine * which thread shall acquire the mutex. (In the case of PTHREAD_MUTEX_RECURSIVE * mutexes, the mutex becomes available when the count reaches zero and the * calling thread no longer has any locks on this mutex). * * If a signal is delivered to a thread waiting for a mutex, upon return from * the signal handler the thread resumes waiting for the mutex as if it was * not interrupted. * * Parameters: * None * * Return Value: * None * * Assumptions: * ****************************************************************************/ int pthread_mutex_unlock(FAR pthread_mutex_t *mutex) { int ret = OK; sdbg("mutex=0x%p\n", mutex); if (!mutex) { ret = EINVAL; } else { /* Make sure the semaphore is stable while we make the following * checks. This all needs to be one atomic action. */ sched_lock(); /* Does the calling thread own the semaphore? */ if (mutex->pid != (int)getpid()) { /* No... return an error (default behavior is like PTHREAD_MUTEX_ERRORCHECK) */ sdbg("Holder=%d returning EPERM\n", mutex->pid); ret = EPERM; } /* Yes, the caller owns the semaphore.. Is this a recursive mutex? */ #ifdef CONFIG_MUTEX_TYPES else if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->nlocks > 1) { /* This is a recursive mutex and we there are multiple locks held. Retain * the mutex lock, just decrement the count of locks held, and return * success. */ mutex->nlocks--; } #endif /* This is either a non-recursive mutex or is the outermost unlock of * a recursive mutex. */ else { /* Nullify the pid and lock count then post the semaphore */ mutex->pid = -1; #ifdef CONFIG_MUTEX_TYPES mutex->nlocks = 0; #endif ret = pthread_givesemaphore((sem_t*)&mutex->sem); } sched_unlock(); } sdbg("Returning %d\n", ret); return ret; }