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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;
}
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