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Diffstat (limited to 'nuttx/sched/pthread_mutexlock.c')
-rw-r--r-- | nuttx/sched/pthread_mutexlock.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/nuttx/sched/pthread_mutexlock.c b/nuttx/sched/pthread_mutexlock.c new file mode 100644 index 000000000..7681d771a --- /dev/null +++ b/nuttx/sched/pthread_mutexlock.c @@ -0,0 +1,187 @@ +/**************************************************************************** + * sched/pthread_mutexlock.c + * + * Copyright (C) 2007-2009 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * 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 <nuttx/config.h> + +#include <unistd.h> +#include <pthread.h> +#include <sched.h> +#include <errno.h> +#include <debug.h> + +#include "pthread_internal.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Type Declarations + ****************************************************************************/ + +/**************************************************************************** + * Global Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: pthread_mutex_lock + * + * Description: + * The mutex object referenced by mutex is locked by calling + * pthread_mutex_lock(). If the mutex is already locked, the calling thread + * blocks until the mutex becomes available. This operation returns with the + * mutex object referenced by mutex in the locked state with the calling + * thread as its owner. + * + * If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not + * provided. Attempting to relock the mutex causes deadlock. If a thread + * attempts to unlock a mutex that it has not locked or a mutex which is + * unlocked, undefined behavior results. + * + * If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is + * provided. If a thread attempts to relock a mutex that it has already + * locked, an error will be returned. If a thread attempts to unlock a + * mutex that it has not locked or a mutex which is unlocked, an error will + * be returned. + * + * If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains + * the concept of a lock count. When a thread successfully acquires a mutex + * for the first time, the lock count is set to one. Every time a thread + * relocks this mutex, the lock count is incremented by one. Each time the + * thread unlocks the mutex, the lock count is decremented by one. When the + * lock count reaches zero, the mutex becomes available for other threads to + * acquire. If a thread attempts to unlock a mutex that it has not locked or + * a mutex which is unlocked, an error will be returned. + * + * 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: + * mutex - A reference to the mutex to be locked. + * + * Return Value: + * 0 on success or an errno value on failure. Note that the errno EINTR + * is never returned by pthread_mutex_lock(). + * + * Assumptions: + * + ****************************************************************************/ + +int pthread_mutex_lock(FAR pthread_mutex_t *mutex) +{ + int mypid = (int)getpid(); + 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 this task already hold the semaphore? */ + + if (mutex->pid == mypid) + { + /* Yes.. Is this a recursive mutex? */ + +#ifdef CONFIG_MUTEX_TYPES + if (mutex->type == PTHREAD_MUTEX_RECURSIVE) + { + /* Yes... just increment the number of locks held and return success */ + + mutex->nlocks++; + } + else +#endif + { + /* No, then we would deadlock... return an error (default behavior + * is like PTHREAD_MUTEX_ERRORCHECK) + */ + + sdbg("Returning EDEADLK\n"); + ret = EDEADLK; + } + } + else + { + /* Take the semaphore */ + + ret = pthread_takesemaphore((sem_t*)&mutex->sem); + + /* If we succussfully obtained the semaphore, then indicate + * that we own it. + */ + + if (!ret) + { + mutex->pid = mypid; +#ifdef CONFIG_MUTEX_TYPES + mutex->nlocks = 1; +#endif + } + } + + sched_unlock(); + } + + sdbg("Returning %d\n", ret); + return ret; +} + |