281 lines
10 KiB
C
281 lines
10 KiB
C
/****************************************************************************
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* sched/pthread/pthread_mutexlock.c
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*
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* Copyright (C) 2007-2009, 2017, 2019 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <sched.h>
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#include <assert.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/sched.h>
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#include "pthread/pthread.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: pthread_mutex_lock
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*
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* Description:
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* The mutex object referenced by mutex is locked by calling
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* pthread_mutex_lock(). If the mutex is already locked, the calling thread
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* blocks until the mutex becomes available. This operation returns with the
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* mutex object referenced by mutex in the locked state with the calling
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* thread as its owner.
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*
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* If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not
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* provided. Attempting to relock the mutex causes deadlock. If a thread
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* attempts to unlock a mutex that it has not locked or a mutex which is
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* unlocked, undefined behavior results.
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*
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* If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is
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* provided. If a thread attempts to relock a mutex that it has already
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* locked, an error will be returned. If a thread attempts to unlock a
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* mutex that it has not locked or a mutex which is unlocked, an error will
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* be returned.
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*
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* If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains
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* the concept of a lock count. When a thread successfully acquires a mutex
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* for the first time, the lock count is set to one. Every time a thread
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* relocks this mutex, the lock count is incremented by one. Each time the
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* thread unlocks the mutex, the lock count is decremented by one. When the
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* lock count reaches zero, the mutex becomes available for other threads to
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* acquire. If a thread attempts to unlock a mutex that it has not locked or
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* a mutex which is unlocked, an error will be returned.
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*
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* If a signal is delivered to a thread waiting for a mutex, upon return
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* from the signal handler the thread resumes waiting for the mutex as if
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* it was not interrupted.
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*
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* Input Parameters:
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* mutex - A reference to the mutex to be locked.
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*
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* Returned Value:
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* 0 on success or an errno value on failure. Note that the errno EINTR
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* is never returned by pthread_mutex_lock().
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*
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* Assumptions:
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*
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* POSIX Compatibility:
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* - This implementation does not return EAGAIN when the mutex could not be
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* acquired because the maximum number of recursive locks for mutex has
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* been exceeded.
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*
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****************************************************************************/
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int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
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{
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return pthread_mutex_timedlock(mutex, NULL);
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}
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/****************************************************************************
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* Name: pthread_mutex_timedlock
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*
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* Description:
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* The pthread_mutex_timedlock() function will lock the mutex object
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* referenced by mutex. If the mutex is already locked, the calling
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* thread will block until the mutex becomes available as in the
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* pthread_mutex_lock() function. If the mutex cannot be locked without
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* waiting for another thread to unlock the mutex, this wait will be
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* terminated when the specified timeout expires.
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*
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* The timeout will expire when the absolute time specified by
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* abs_timeout passes, as measured by the clock on which timeouts are
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* based (that is, when the value of that clock equals or exceeds
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* abs_timeout), or if the absolute time specified by abs_timeout
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* has already been passed at the time of the call.
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*
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* Input Parameters:
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* mutex - A reference to the mutex to be locked.
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* abs_timeout - max wait time (NULL wait forever)
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*
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* Returned Value:
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* 0 on success or an errno value on failure. Note that the errno EINTR
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* is never returned by pthread_mutex_timedlock().
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* errno is ETIMEDOUT if mutex could not be locked before the specified
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* timeout expired
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*
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* Assumptions:
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*
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* POSIX Compatibility:
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* - This implementation does not return EAGAIN when the mutex could not be
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* acquired because the maximum number of recursive locks for mutex has
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* been exceeded.
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*
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****************************************************************************/
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int pthread_mutex_timedlock(FAR pthread_mutex_t *mutex,
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FAR const struct timespec *abs_timeout)
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{
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int mypid = (int)getpid();
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int ret = EINVAL;
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sinfo("mutex=0x%p\n", mutex);
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DEBUGASSERT(mutex != NULL);
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if (mutex != NULL)
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{
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/* Make sure the semaphore is stable while we make the following
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* checks. This all needs to be one atomic action.
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*/
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sched_lock();
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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/* All mutex types except for NORMAL (and DEFAULT) will return
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* and an error error if the caller does not hold the mutex.
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*/
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if (mutex->type != PTHREAD_MUTEX_NORMAL && mutex->pid == mypid)
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{
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/* Yes.. Is this a recursive mutex? */
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if (mutex->type == PTHREAD_MUTEX_RECURSIVE)
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{
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/* Yes... just increment the number of locks held and return
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* success.
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*/
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if (mutex->nlocks < INT16_MAX)
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{
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mutex->nlocks++;
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ret = OK;
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}
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else
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{
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ret = EOVERFLOW;
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}
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}
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else
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{
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/* No, then we would deadlock... return an error (default
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* behavior is like PTHREAD_MUTEX_ERRORCHECK)
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*
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* NOTE: This is the correct behavior for a 'robust', NORMAL
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* mutex. Compiant behavior for non-robust mutex should not
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* include these checks. In that case, it the deadlock
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* condition should not be detected and the thread should be
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* permitted to deadlock.
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*/
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serr("ERROR: Returning EDEADLK\n");
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ret = EDEADLK;
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}
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}
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else
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#endif /* CONFIG_PTHREAD_MUTEX_TYPES */
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#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
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/* The calling thread does not hold the semaphore. The correct
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* behavior for the 'robust' mutex is to verify that the holder of the
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* mutex is still valid. This is protection from the case
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* where the holder of the mutex has exitted without unlocking it.
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*/
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#ifdef CONFIG_PTHREAD_MUTEX_BOTH
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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/* Include check if this is a NORMAL mutex and that it is robust */
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if (mutex->pid > 0 &&
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((mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 ||
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mutex->type != PTHREAD_MUTEX_NORMAL) &&
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sched_gettcb(mutex->pid) == NULL)
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#else /* CONFIG_PTHREAD_MUTEX_TYPES */
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/* This can only be a NORMAL mutex. Include check if it is robust */
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if (mutex->pid > 0 &&
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(mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 &&
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sched_gettcb(mutex->pid) == NULL)
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#endif /* CONFIG_PTHREAD_MUTEX_TYPES */
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#else /* CONFIG_PTHREAD_MUTEX_ROBUST */
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/* This mutex is always robust, whatever type it is. */
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if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL)
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#endif
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{
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DEBUGASSERT(mutex->pid != 0); /* < 0: available, >0 owned, ==0 error */
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DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0);
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/* A thread holds the mutex, but there is no such thread. POSIX
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* requires that the 'robust' mutex return EOWNERDEAD in this
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* case. It is then the caller's responsibility to call
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* pthread_mutx_consistent() to fix the mutex.
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*/
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mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT;
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ret = EOWNERDEAD;
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}
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else
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#endif /* !CONFIG_PTHREAD_MUTEX_UNSAFE */
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{
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/* Take the underlying semaphore, waiting if necessary. NOTE that
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* is required to deadlock for the case of the non-robust NORMAL
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* or default mutex.
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*/
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ret = pthread_mutex_take(mutex, NULL, true);
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/* If we successfully obtained the semaphore, then indicate
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* that we own it.
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*/
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if (ret == OK)
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{
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mutex->pid = mypid;
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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mutex->nlocks = 1;
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#endif
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}
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}
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sched_unlock();
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}
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sinfo("Returning %d\n", ret);
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return ret;
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}
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