nuttx/sched/pthread/pthread_mutex.c

/****************************************************************************
 * sched/pthread/pthread_mutex.c
 *
 *   Copyright (C) 2017 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 <stdbool.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>

#include <nuttx/irq.h>
#include <nuttx/sched.h>

#include "sched/sched.h"
#include "pthread/pthread.h"

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_mutex_add
 *
 * Description:
 *   Add the mutex to the list of mutexes held by this thread.
 *
 * Parameters:
 *  mutex - The mux to be locked
 *
 * Return Value:
 *   None
 *
 ****************************************************************************/

static void pthread_mutex_add(FAR struct pthread_mutex_s *mutex)
{
  FAR struct pthread_tcb_s *rtcb = (FAR struct pthread_tcb_s *)this_task();
  irqstate_t flags;

  DEBUGASSERT(mutex->flink == NULL);

  /* Add the mutex to the list of mutexes held by this task */

  flags        = enter_critical_section();
  mutex->flink = rtcb->mhead;
  rtcb->mhead  = mutex;
  leave_critical_section(flags);
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_mutex_take
 *
 * Description:
 *   Take the pthread_mutex, waiting if necessary.  If successful, add the
 *   mutex to the list of mutexes held by this thread.
 *
 * Parameters:
 *  mutex - The mux to be locked
 *  intr  - false: ignore EINTR errors when locking; true tread EINTR as
 *          other errors by returning the errno value
 *
 * Return Value:
 *   0 on success or an errno value on failure.
 *
 ****************************************************************************/

int pthread_mutex_take(FAR struct pthread_mutex_s *mutex, bool intr)
{
  int ret = EINVAL;

  /* Verify input parameters */

  DEBUGASSERT(mutex != NULL);
  if (mutex != NULL)
    {
      /* Make sure that no unexpected context switches occur */

      sched_lock();

      /* Error out if the mutex is already in an inconsistent state. */

      if ((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0)
        {
          ret = EOWNERDEAD;
        }
      else
        {
          /* Take semaphore underlying the mutex */

          ret = pthread_takesemaphore(&mutex->sem, intr);
          if (ret < OK)
            {
              ret = get_errno();
            }
          else
            {
              /* Check if the holder of the mutex has terminated without
               * releasing.  In that case, the state of the mutex is
               * inconsistent and we return EOWNERDEAD.
               */

              if ((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0)
                {
                  ret = EOWNERDEAD;
                }

              /* Add the mutex to the list of mutexes held by this task */

              else
                {
                  pthread_mutex_add(mutex);
                }
            }
        }

      sched_unlock();
    }

  return ret;
}

/****************************************************************************
 * Name: pthread_mutex_trytake
 *
 * Description:
 *   Try to take the pthread_mutex without waiting.  If successful, add the
 *   mutex to the list of mutexes held by this thread.
 *
 * Parameters:
 *  mutex - The mux to be locked
 *  intr  - false: ignore EINTR errors when locking; true tread EINTR as
 *          other errors by returning the errno value
 *
 * Return Value:
 *   0 on success or an errno value on failure.
 *
 ****************************************************************************/

int pthread_mutex_trytake(FAR struct pthread_mutex_s *mutex)
{
  int ret = EINVAL;

  /* Verify input parameters */

  DEBUGASSERT(mutex != NULL);
  if (mutex != NULL)
    {
      /* Make sure that no unexpected context switches occur */

      sched_lock();

      /* Error out if the mutex is already in an inconsistent state. */

      if ((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0)
        {
          ret = EOWNERDEAD;
        }
      else
        {
          /* Try to take the semaphore underlying the mutex */

          ret = sem_trywait(&mutex->sem);
          if (ret < OK)
            {
              ret = get_errno();
            }
          else
            {
              /* Add the mutex to the list of mutexes held by this task */

              pthread_mutex_add(mutex);
            }
        }

      sched_unlock();
    }

  return ret;
}

/****************************************************************************
 * Name: pthread_mutex_give
 *
 * Description:
 *   Take the pthread_mutex and, if successful, add the mutex to the ist of
 *   mutexes held by this thread.
 *
 * Parameters:
 *  mutex - The mux to be unlocked
 *
 * Return Value:
 *   0 on success or an errno value on failure.
 *
 ****************************************************************************/

int pthread_mutex_give(FAR struct pthread_mutex_s *mutex)
{
  FAR struct pthread_mutex_s *curr;
  FAR struct pthread_mutex_s *prev;
  int ret = EINVAL;

  /* Verify input parameters */

  DEBUGASSERT(mutex != NULL);
  if (mutex != NULL)
    {
      FAR struct pthread_tcb_s *rtcb = (FAR struct pthread_tcb_s *)this_task();
      irqstate_t flags;

      flags = enter_critical_section();

      /* Remove the mutex from the list of mutexes held by this task */

      for (prev = NULL, curr = rtcb->mhead;
           curr != NULL && curr != mutex;
           prev = curr, curr = curr->flink);

      DEBUGASSERT(curr == mutex);

      /* Remove the mutex from the list.  prev == NULL means that the mutex
       * to be removed is at the head of the list.
       */

      if (prev == NULL)
        {
          rtcb->mhead = mutex->flink;
        }
      else
        {
          prev->flink = mutex->flink;
        }

      mutex->flink = NULL;
      leave_critical_section(flags);

      /* Now release the underlying semaphore */

      ret = pthread_givesemaphore(&mutex->sem);
    }

  return ret;
}