| /**************************************************************************** |
| * sched/pthread_mutexlock.c |
| * |
| * Copyright (C) 2007-2009 Gregory Nutt. All rights reserved. |
| * Author: Gregory Nutt <spudmonkey@racsa.co.cr> |
| * |
| * 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 |
| ****************************************************************************/ |
| |
| /**************************************************************************** |
| * Function: 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; |
| } |
| |