pthread_cond_clockwait implementation

condclockwait.c

/**
 * @file
 *
 * @ingroup POSIXAPI
 *
 * @brief Waiting on a Condition
 */

/* 
* Copyright (C) 2021 Matthew Joyce
*
* 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.
*
* 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.
*/

/* Defining to have access to function prototype in libc/include/pthread.h */
#define _GNU_SOURCE

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/posix/condimpl.h>
#include <rtems/score/todimpl.h>

/*
 *  pthread_cond_clockwait() appears in the Issue 8 POSIX Standard
 */
int pthread_cond_clockwait(
  pthread_cond_t             *restrict cond,
  pthread_mutex_t           *restrict mutex,
  clockid_t                        clock_id,
  const struct timespec    *restrict abstime
)
{
  /* 
   * POSIX Issue 8 does not specify that EINVAL is returned when abstime
   * equals NULL. 
   */
  if ( abstime == NULL ) {
    return EINVAL; 
  }

  /* 
   * POSIX Issue 8 specifies that EINVAL is returned when the clock is not
   * supported.  
   */
  if ( clock_id != CLOCK_REALTIME ) {
    if ( clock_id != CLOCK_MONOTONIC ) {
      return EINVAL; 
    }
  }
  
  return _POSIX_Condition_variables_Wait_support(
    cond,
    mutex,
    clock_id,
    abstime
  );
}

condwaitsupp.c

/**
 * @file
 *
 * @ingroup POSIX_COND_VARS
 *
 * @brief POSIX Condition Variables Wait Support
 */

/*
 *  COPYRIGHT (c) 1989-2014.
 *  On-Line Applications Research Corporation (OAR).
 *  COPYRIGHT (c) 2021.
 *  Matthew Joyce.
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/posix/condimpl.h>
#include <rtems/posix/posixapi.h>
#include <rtems/score/assert.h>
#include <rtems/score/statesimpl.h>
#include <rtems/score/status.h>
#include <rtems/score/threaddispatch.h>

#ifdef CLOCK_REALTIME_COARSE
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_REALTIME_COARSE),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_PROCESS_CPUTIME_ID
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_PROCESS_CPUTIME_ID),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_REALTIME
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_REALTIME),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif 
#ifdef CLOCK_THREAD_CPUTIME_ID
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_THREAD_CPUTIME_ID),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_MONOTONIC
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_MONOTONIC),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_MONOTONIC_RAW
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_MONOTONIC_RAW),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_MONOTONIC_COARSE
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_MONOTONIC_COARSE),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_BOOTTIME
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_BOOTTIME),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_REALTIME_ALARM
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_REALTIME_ALARM),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif
#ifdef CLOCK_BOOTTIME_ALARM
  RTEMS_STATIC_ASSERT(
    ( CLOCK_NOT_SPECIFIED != CLOCK_BOOTTIME_ALARM),
     "CLOCK_NOT_SPECIFIED conflicts with existing POSIX defined clock/n" ); 
#endif 

static void _POSIX_Condition_variables_Mutex_unlock(
  Thread_queue_Queue   *queue,
  Thread_Control       *the_thread,
  Thread_queue_Context *queue_context
)
{
  POSIX_Condition_variables_Control *the_cond;
  int                                mutex_error;

  the_cond = POSIX_CONDITION_VARIABLE_OF_THREAD_QUEUE_QUEUE( queue );

  mutex_error = pthread_mutex_unlock( the_cond->mutex );
  if ( mutex_error != 0 ) {
    /*
     *  Historically, we ignored the unlock status since the behavior
     *  is undefined by POSIX. But GNU/Linux returns EPERM in this
     *  case, so we follow their lead.
     */
    _Assert( mutex_error == EINVAL || mutex_error == EPERM );
    _Thread_Continue( the_thread, STATUS_NOT_OWNER );
  }
}

static void _POSIX_Condition_variables_Enqueue_no_timeout(
  Thread_queue_Queue   *queue,
  Thread_Control       *the_thread,
  Per_CPU_Control      *cpu_self,
  Thread_queue_Context *queue_context
)
{
  _POSIX_Condition_variables_Mutex_unlock( queue, the_thread, queue_context );
}

static void _POSIX_Condition_variables_Enqueue_with_timeout_monotonic(
  Thread_queue_Queue   *queue,
  Thread_Control       *the_thread,
  Per_CPU_Control      *cpu_self,
  Thread_queue_Context *queue_context
)
{
  _Thread_queue_Add_timeout_monotonic_timespec(
    queue,
    the_thread,
    cpu_self,
    queue_context
  );
  _POSIX_Condition_variables_Mutex_unlock( queue, the_thread, queue_context );
}

static void _POSIX_Condition_variables_Enqueue_with_timeout_realtime(
  Thread_queue_Queue   *queue,
  Thread_Control       *the_thread,
  Per_CPU_Control      *cpu_self,
  Thread_queue_Context *queue_context
)
{
  _Thread_queue_Add_timeout_realtime_timespec(
    queue,
    the_thread,
    cpu_self,
    queue_context
  );
  _POSIX_Condition_variables_Mutex_unlock( queue, the_thread, queue_context );
}

int _POSIX_Condition_variables_Wait_support(
  pthread_cond_t             *restrict cond,
  pthread_mutex_t           *restrict mutex,
  clockid_t                        clock_id,
  const struct timespec    *restrict abstime
)
{
  POSIX_Condition_variables_Control      *the_cond;
  unsigned long                          flags;
  Thread_queue_Context                   queue_context;
  int                                    error;
  Thread_Control                         *executing;
  pthread_condattr_t                     attr; 

  the_cond = _POSIX_Condition_variables_Get( cond );
  POSIX_CONDITION_VARIABLES_VALIDATE_OBJECT( the_cond, flags );

  _Thread_queue_Context_initialize( &queue_context );

  _Thread_queue_Context_set_timeout_argument( &queue_context, abstime, true );

  error = pthread_condattr_init( &attr );
  _Assert( error == 0 );

  /* 
   * If the parameter clock_id is not specified, then the clock from the 
   * condition attributes shall be used.
   */
  if ( clock_id == CLOCK_NOT_SPECIFIED ) {
    error = pthread_condattr_getclock( &attr, &clock_id );
    _Assert( error == 0 ); 
  }

  /* 
   * Now we have the desired clock_id, no matter whether it came from
   * cond_timedwait or cond_clockwait. If abstime is specified, we use the 
   * clock_id to set the correct timeout. 
   */
  if ( abstime != NULL ) {
    /* 
     * We have already validated supported clocks in condclockwait.c.
     * if clock_id is not CLOCK_MONOTONIC, then it is CLOCK_REALTIME. 
     */
    if ( clock_id == CLOCK_MONOTONIC ) {
      _Thread_queue_Context_set_enqueue_callout(
        &queue_context,
        _POSIX_Condition_variables_Enqueue_with_timeout_monotonic
      );
    }  
    
    else {
        _Thread_queue_Context_set_enqueue_callout(
        &queue_context,
        _POSIX_Condition_variables_Enqueue_with_timeout_realtime
      );
    }
  }

  /* 
   * Otherwise, if the abstime parameter is NULL, this is a call to 
   * pthread_cond_wait and no timeout is necessary.
   */
  else {
    _Thread_queue_Context_set_enqueue_callout(
      &queue_context,
      _POSIX_Condition_variables_Enqueue_no_timeout
    );
  }

  executing = _POSIX_Condition_variables_Acquire( the_cond, &queue_context );

  if (
    the_cond->mutex != POSIX_CONDITION_VARIABLES_NO_MUTEX
      && the_cond->mutex != mutex
  ) {
    _POSIX_Condition_variables_Release( the_cond, &queue_context );
    return EINVAL;
  }
  the_cond->mutex = mutex;
  _Thread_queue_Context_set_thread_state(
    &queue_context,
    STATES_WAITING_FOR_CONDITION_VARIABLE
  );
  _Thread_queue_Enqueue(
    &the_cond->Queue.Queue,
    POSIX_CONDITION_VARIABLES_TQ_OPERATIONS,
    executing,
    &queue_context
  );
  
  error = _POSIX_Get_error_after_wait( executing );
  /*
   *  If the thread is interrupted, while in the thread queue, by
   *  a POSIX signal, then pthread_cond_wait returns spuriously,
   *  according to the POSIX standard. It means that pthread_cond_wait
   *  returns a success status, except for the fact that it was not
   *  woken up a pthread_cond_signal() or a pthread_cond_broadcast().
   */
  if ( error == EINTR ) {
    error = 0;
  }
  /*
   *  When we get here the dispatch disable level is 0.
   */
  if ( error != EPERM ) {
    int mutex_error;

    mutex_error = pthread_mutex_lock( mutex );
    if ( mutex_error != 0 ) {
      _Assert( mutex_error == EINVAL );
      error = EINVAL;
    }
  }
  return error;
}

My implementation of the new POSIX standard method pthread_cond_clockwait for the RTEMS real-time operating system (RTOS).