root/include/linux/mqueue.h

INCLUDED FROM

/* Copyright (C) 2003 Krzysztof Benedyczak & Michal Wronski

   This program 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 2.1 of the License, or (at your option) any later version.

   It 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 software; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _LINUX_MQUEUE_H
#define _LINUX_MQUEUE_H

#define MQ_PRIO_MAX     32768
/* per-uid limit of kernel memory used by mqueue, in bytes */
#define MQ_BYTES_MAX    819200

struct mq_attr {
        long    mq_flags;       /* message queue flags                  */
        long    mq_maxmsg;      /* maximum number of messages           */
        long    mq_msgsize;     /* maximum message size                 */
        long    mq_curmsgs;     /* number of messages currently queued  */
        long    __reserved[4];  /* ignored for input, zeroed for output */
};

/*
 * SIGEV_THREAD implementation:
 * SIGEV_THREAD must be implemented in user space. If SIGEV_THREAD is passed
 * to mq_notify, then
 * - sigev_signo must be the file descriptor of an AF_NETLINK socket. It's not
 *   necessary that the socket is bound.
 * - sigev_value.sival_ptr must point to a cookie that is NOTIFY_COOKIE_LEN
 *   bytes long.
 * If the notification is triggered, then the cookie is sent to the netlink
 * socket. The last byte of the cookie is replaced with the NOTIFY_?? codes:
 * NOTIFY_WOKENUP if the notification got triggered, NOTIFY_REMOVED if it was
 * removed, either due to a close() on the message queue fd or due to a
 * mq_notify() that removed the notification.
 */
#define NOTIFY_NONE     0
#define NOTIFY_WOKENUP  1
#define NOTIFY_REMOVED  2

#define NOTIFY_COOKIE_LEN       32

#endif