107 lines
2.5 KiB
C
107 lines
2.5 KiB
C
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/* Copyright 2002, Red Hat Inc. */
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#include <mqueue.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sys/ipc.h>
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#include <sys/sem.h>
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#include <string.h>
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#include "internals.h"
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#include <sys/lock.h>
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#include "mqlocal.h"
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static void *mq_notify_process (void *);
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void
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__cleanup_mq_notify (struct libc_mq *info)
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{
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struct sembuf sb4 = {4, 1, 0};
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/* kill notification thread and allow other processes to set a notification */
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pthread_cancel ((pthread_t)info->th);
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semop (info->semid, &sb4, 1);
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}
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static void *
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mq_notify_process (void *arg)
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{
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struct libc_mq *info = (struct libc_mq *)arg;
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struct sembuf sb3[2] = {{3, 0, 0}, {5, 0, 0}};
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struct sembuf sb4 = {4, 1, 0};
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int rc;
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/* wait until queue is empty */
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while (!(rc = semop (info->semid, sb3, 1)) && errno == EINTR)
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/* empty */ ;
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if (!rc)
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{
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/* now wait until there are 0 readers and the queue has something in it */
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sb3[0].sem_op = -1;
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while (!(rc = semop (info->semid, sb3, 2)) && errno == EINTR)
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/* empty */ ;
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/* restore value since we have not actually performed a read */
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sb3[0].sem_op = 1;
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semop (info->semid, sb3, 1);
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/* perform desired notification - either run function in this thread or pass signal */
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if (!rc)
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{
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if (info->sigevent->sigev_notify == SIGEV_SIGNAL)
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raise (info->sigevent->sigev_signo);
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else if (info->sigevent->sigev_notify == SIGEV_THREAD)
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info->sigevent->sigev_notify_function (info->sigevent->sigev_value);
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/* allow other processes to now mq_notify */
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semop (info->semid, &sb4, 1);
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}
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}
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pthread_exit (NULL);
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}
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int
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mq_notify (mqd_t msgid, const struct sigevent *notification)
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{
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struct libc_mq *info;
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struct sembuf sb4 = {4, -1, IPC_NOWAIT};
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int rc;
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pthread_attr_t *attr = NULL;
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info = __find_mq (msgid);
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if (info == NULL)
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{
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errno = EBADF;
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return -1;
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}
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/* get notification lock */
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rc = semop (info->semid, &sb4, 1);
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if (rc == -1)
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{
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errno = EBUSY;
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return -1;
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}
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/* to get the notification running we use a pthread - if the user has requested
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an action in a pthread, we use the user's attributes when setting up the thread */
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info->sigevent = (struct sigevent *)notification;
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if (info->sigevent->sigev_notify == SIGEV_THREAD)
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attr = (pthread_attr_t *)info->sigevent->sigev_notify_attributes;
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rc = pthread_create ((pthread_t *)&info->th, attr, mq_notify_process, (void *)info);
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if (rc != 0)
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rc = -1;
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else
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info->cleanup_notify = &__cleanup_mq_notify;
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return rc;
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}
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