path: root/sched.c

/*
 * sched.c
 * 
 * Description:
 * POSIX thread functions that deal with thread scheduling.
 *
 * --------------------------------------------------------------------------
 *
 *      Pthreads-win32 - POSIX Threads Library for Win32
 *      Copyright(C) 1998 John E. Bossom
 *      Copyright(C) 1999,2002 Pthreads-win32 contributors
 * 
 *      Contact Email: rpj@ise.canberra.edu.au
 * 
 *      The current list of contributors is contained
 *      in the file CONTRIBUTORS included with the source
 *      code distribution. The list can also be seen at the
 *      following World Wide Web location:
 *      http://sources.redhat.com/pthreads-win32/contributors.html
 * 
 *      This library is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU Lesser General Public
 *      License as published by the Free Software Foundation; either
 *      version 2 of the License, or (at your option) any later version.
 * 
 *      This library is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *      Lesser General Public License for more details.
 * 
 *      You should have received a copy of the GNU Lesser General Public
 *      License along with this library in the file COPYING.LIB;
 *      if not, write to the Free Software Foundation, Inc.,
 *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include "pthread.h"
#include "implement.h"
#include "sched.h"

static int
is_attr(const pthread_attr_t *attr)
{
  return (attr == NULL || 
	  *attr == NULL || 
	  (*attr)->valid != PTW32_ATTR_VALID) ? 1 : 0;
}


int
pthread_attr_setschedpolicy(pthread_attr_t *attr,
                            int policy)
{
  if (is_attr(attr) != 0)
    {
      return EINVAL;
    }

  if (policy != SCHED_OTHER)
    {
      return ENOTSUP;
    }

  return 0;
}


int
pthread_attr_getschedpolicy(pthread_attr_t *attr,
                            int * policy)
{
  if (is_attr(attr) != 0 || policy == NULL)
    {
      return EINVAL;
    }

  /*
   * Validate the policy arg.
   * Check that a policy constant wasn't passed rather than &policy.
   */
  if (policy <= (int *) SCHED_MAX)
    {
      return EINVAL;
    }

  *policy = SCHED_OTHER;

  return 0;
}


int
pthread_attr_setschedparam(pthread_attr_t *attr,
			   const struct sched_param *param)
{
  int priority;

  if (is_attr(attr) != 0 || param == NULL)
    {
      return EINVAL;
    }

  priority = param->sched_priority;

  /* Validate priority level. */
  if (priority < sched_get_priority_min(SCHED_OTHER) ||
      priority > sched_get_priority_max(SCHED_OTHER))
    {
      return EINVAL;
    }

  memcpy(&(*attr)->param, param, sizeof(*param));
  return 0;
}


int 
pthread_attr_getschedparam(const pthread_attr_t *attr,
                           struct sched_param *param)
{
  if (is_attr(attr) != 0 || param == NULL)
    {
      return EINVAL;
    }
  
  memcpy(param, &(*attr)->param, sizeof(*param));
  return 0;
}


int
pthread_attr_setinheritsched(pthread_attr_t * attr,
                             int inheritsched)
{
  if (is_attr(attr) != 0)
    {
      return EINVAL;
    }

  if (PTHREAD_INHERIT_SCHED != inheritsched
      && PTHREAD_EXPLICIT_SCHED != inheritsched)
    {
      return EINVAL;
    }

  (*attr)->inheritsched = inheritsched;
  return 0;
}


int
pthread_attr_getinheritsched(pthread_attr_t * attr,
                             int * inheritsched)
{
  if (is_attr(attr) != 0 || inheritsched == NULL)
    {
      return EINVAL;
    }

  *inheritsched = (*attr)->inheritsched;
  return 0;
}


int
pthread_setschedparam(pthread_t thread, int policy,
			  const struct sched_param *param)
{
  int prio;

  /* Validate the thread id. */
  if (thread == NULL || thread->threadH == 0)
    {
      return EINVAL;
    }

  /* Validate the scheduling policy. */
  if (policy < SCHED_MIN || policy > SCHED_MAX)
    {
      return EINVAL;
    }

  /* Ensure the policy is SCHED_OTHER. */
  if (policy != SCHED_OTHER)
    {
      return ENOTSUP;
    }

  prio = param->sched_priority;

  /* Validate priority level. */
  if (prio < sched_get_priority_min(policy) ||
      prio > sched_get_priority_max(policy))
    {
      return EINVAL;
    }

  /* This is practically guaranteed to return TRUE. */
  (void) SetThreadPriority(thread->threadH, prio);

  return 0;
}


int
pthread_getschedparam(pthread_t thread, int *policy,
			  struct sched_param *param)
{
  int prio;

  /* Validate the thread id. */
  if (thread == NULL || thread->threadH == 0)
    {
      return EINVAL;
    }

  /*
   * Validate the policy and param args.
   * Check that a policy constant wasn't passed rather than &policy.
   */
  if (policy <= (int *) SCHED_MAX || param == NULL)
    {
      return EINVAL;
    }

  /* Fill out the policy. */
  *policy = SCHED_OTHER;

  /* Fill out the sched_param structure. */
  prio = GetThreadPriority(thread->threadH);
  if (prio == THREAD_PRIORITY_ERROR_RETURN)
    {
      return EINVAL;
    }
  
  param->sched_priority = prio;
  return 0;
}


/*
 * On Windows98, THREAD_PRIORITY_LOWEST is (-2) and 
 * THREAD_PRIORITY_HIGHEST is 2, and everything works just fine.
 * 
 * On WinCE 3.0, it so happen that THREAD_PRIORITY_LOWEST is 5
 * and THREAD_PRIORITY_HIGHEST is 1 (yes, I know, it is funny:
 * highest priority use smaller numbers) and the following happens:
 * 
 * sched_get_priority_min() returns 5
 * sched_get_priority_max() returns 1
 */


int
sched_get_priority_max(int policy)
{
  if (policy < SCHED_MIN || policy > SCHED_MAX)
    {
      return EINVAL;
    }

#if (THREAD_PRIORITY_LOWEST > THREAD_PRIORITY_NORMAL)
  /* WinCE? */
  return PTW32_MAX(THREAD_PRIORITY_IDLE, THREAD_PRIORITY_TIME_CRITICAL);
#else
  /* This is independent of scheduling policy in Win32. */
  return PTW32_MAX(THREAD_PRIORITY_IDLE, THREAD_PRIORITY_TIME_CRITICAL);
#endif
}


int
sched_get_priority_min(int policy)
{
  if (policy < SCHED_MIN || policy > SCHED_MAX)
    {
      return EINVAL;
    }

#if (THREAD_PRIORITY_LOWEST > THREAD_PRIORITY_NORMAL)
  /* WinCE? */
  return PTW32_MIN(THREAD_PRIORITY_IDLE, THREAD_PRIORITY_TIME_CRITICAL);
#else
  /* This is independent of scheduling policy in Win32. */
  return PTW32_MIN(THREAD_PRIORITY_IDLE, THREAD_PRIORITY_TIME_CRITICAL);
#endif
}


int
sched_setscheduler(pid_t pid, int policy)
{
  /*
   * Win32 only has one policy which we call SCHED_OTHER.
   * However, we try to provide other valid side-effects
   * such as EPERM and ESRCH errors. Choosing to check
   * for a valid policy last allows us to get the most value out
   * of this function.
   */
  if (0 != pid)
    {
      int selfPid = (int) GetCurrentProcessId();

      if (pid != selfPid)
        {
          HANDLE h = OpenProcess(PROCESS_SET_INFORMATION, FALSE, (DWORD) pid);

          if (NULL == h)
            {
              errno = (GetLastError() == (0xFF & ERROR_ACCESS_DENIED)) ? EPERM : ESRCH;
              return -1;
            }
        }
    }

  if (SCHED_OTHER != policy)
    {
      errno = ENOSYS;
      return -1;
    }

  /*
   * Don't set anything because there is nothing to set.
   * Just return the current (the only possible) value.
   */
  return SCHED_OTHER;
}


int
sched_getscheduler(pid_t pid)
{
  /*
   * Win32 only has one policy which we call SCHED_OTHER.
   * However, we try to provide other valid side-effects
   * such as EPERM and ESRCH errors.
   */
  if (0 != pid)
    {
      int selfPid = (int) GetCurrentProcessId();

      if (pid != selfPid)
        {
          HANDLE h = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, (DWORD) pid);

          if (NULL == h)
            {
              errno = (GetLastError() == (0xFF & ERROR_ACCESS_DENIED)) ? EPERM : ESRCH;
              return -1;
            }
        }
    }

  return SCHED_OTHER;
}


int
sched_yield(void)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function indicates that the calling thread is
      *      willing to give up some time slices to other threads.
      *
      * PARAMETERS
      *      N/A
      *
      *
      * DESCRIPTION
      *      This function indicates that the calling thread is
      *      willing to give up some time slices to other threads.
      *      NOTE: Since this is part of POSIX 1003.1b
      *                (realtime extensions), it is defined as returning
      *                -1 if an error occurs and sets errno to the actual
      *                error.
      *
      * RESULTS
      *              0               successfully created semaphore,
      *              ENOSYS          sched_yield not supported,
      *
      * ------------------------------------------------------
      */
{
  Sleep(0);

  return 0;
}