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/* Copyright 2002, Red Hat Inc. */

#include <mqueue.h>

#include <unistd.h>

#include <errno.h>

#include <sys/ipc.h>

#include <sys/sem.h>

#include <string.h>

#include "internals.h"

#include <sys/lock.h>

#include "mqlocal.h"

static void *mq_notify_process (void *);

void

__cleanup_mq_notify (struct libc_mq *info)

{

  struct sembuf sb4 = {4, 1, 0};

  /* kill notification thread and allow other processes to set a notification */

  pthread_cancel ((pthread_t)info->th);

  semop (info->semid, &sb4, 1);

}

static void *

mq_notify_process (void *arg)

{

  struct libc_mq *info = (struct libc_mq *)arg;

  struct sembuf sb3[2] = {{3, 0, 0}, {5, 0, 0}};

  struct sembuf sb4 = {4, 1, 0};

  int rc;

  /* wait until queue is empty */

  while (!(rc = semop (info->semid, sb3, 1)) && errno == EINTR)

    /* empty */ ;

  if (!rc)

    {

      /* now wait until there are 0 readers and the queue has something in it */

      sb3[0].sem_op = -1;

      while (!(rc = semop (info->semid, sb3, 2)) && errno == EINTR)

        /* empty */ ;

      /* restore value since we have not actually performed a read */

      sb3[0].sem_op = 1;

      semop (info->semid, sb3, 1);

      /* perform desired notification - either run function in this thread or pass signal */

      if (!rc)

        {

          if (info->sigevent->sigev_notify == SIGEV_SIGNAL)

            raise (info->sigevent->sigev_signo);

          else if (info->sigevent->sigev_notify == SIGEV_THREAD)

            info->sigevent->sigev_notify_function (info->sigevent->sigev_value);

          /* allow other processes to now mq_notify */

          semop (info->semid, &sb4, 1);

        }

    }

  pthread_exit (NULL);

}

int

mq_notify (mqd_t msgid, const struct sigevent *notification)

{

  struct libc_mq *info;

  struct sembuf sb4 = {4, -1, IPC_NOWAIT};

  int rc;

  pthread_attr_t *attr = NULL;

  info = __find_mq (msgid);

  if (info == NULL)

    {

      errno = EBADF;

      return -1;

    }

  /* get notification lock */

  rc = semop (info->semid, &sb4, 1);

  if (rc == -1)

    {

      errno = EBUSY;

      return -1;

    }

  /* to get the notification running we use a pthread - if the user has requested

     an action in a pthread, we use the user's attributes when setting up the thread */

  info->sigevent = (struct sigevent *)notification;

  if (info->sigevent->sigev_notify == SIGEV_THREAD)

    attr = (pthread_attr_t *)info->sigevent->sigev_notify_attributes;

  rc = pthread_create ((pthread_t *)&info->th, attr, mq_notify_process, (void *)info);

  if (rc != 0)

    rc = -1;

  else

    info->cleanup_notify = &__cleanup_mq_notify;

  return rc;

}