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diff --git a/lib/libsys/mq_notify.2 b/lib/libsys/mq_notify.2 new file mode 100644 index 000000000000..f2bf7aa6ebf4 --- /dev/null +++ b/lib/libsys/mq_notify.2 @@ -0,0 +1,163 @@ +.\" Copyright (c) 2005 David Xu <davidxu@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice(s), this list of conditions and the following disclaimer as +.\" the first lines of this file unmodified other than the possible +.\" addition of one or more copyright notices. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice(s), this list of conditions and the following disclaimer in +.\" the documentation and/or other materials provided with the +.\" distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY +.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE +.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR +.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, +.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE +.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, +.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\" Portions of this text are reprinted and reproduced in electronic form +.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- +.\" Portable Operating System Interface (POSIX), The Open Group Base +.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of +.\" Electrical and Electronics Engineers, Inc and The Open Group. In the +.\" event of any discrepancy between this version and the original IEEE and +.\" The Open Group Standard, the original IEEE and The Open Group Standard is +.\" the referee document. The original Standard can be obtained online at +.\" http://www.opengroup.org/unix/online.html. +.\" +.Dd July 15, 2016 +.Dt MQ_NOTIFY 2 +.Os +.Sh NAME +.Nm mq_notify +.Nd "notify process that a message is available (REALTIME)" +.Sh LIBRARY +.Lb librt +.Sh SYNOPSIS +.In mqueue.h +.Ft int +.Fn mq_notify "mqd_t mqdes" "const struct sigevent *notification" +.Sh DESCRIPTION +If the argument notification is not +.Dv NULL , +this system call will register the calling process to be notified of message +arrival at an empty message queue associated with the specified message +queue descriptor, +.Fa mqdes . +The notification specified by the +.Fa notification +argument will be sent to +the process when the message queue transitions from empty to non-empty. +At any time, only one process may be registered for notification by a +message queue. +If the calling process or any other process has already +registered for notification of message arrival at the specified message +queue, subsequent attempts to register for that message queue will fail. +.Pp +The +.Fa notification +argument points to a +.Vt sigevent +structure that defines how the calling process will be notified. +If +.Fa notification->sigev_notify +is +.Dv SIGEV_NONE , +then no signal will be posted, but the error status and the return status +for the operation will be set appropriately. +For +.Dv SIGEV_SIGNO +and +.Dv SIGEV_THREAD_ID +notifications, +the signal specified in +.Fa notification->sigev_signo +will be sent to the calling process +.Pq Dv SIGEV_SIGNO +or to the thread whose LWP ID is +.Fa notification->sigev_notify_thread_id +.Pq Dv SIGEV_THREAD_ID . +The information for the queued signal will include: +.Bl -column ".Va si_value" +.It Sy Member Ta Sy Value +.It Va si_code Ta Dv SI_MESGQ +.It Va si_value Ta +the value stored in +.Fa notification->sigev_value +.It Va si_mqd Ta Fa mqdes +.El +.Pp +If +.Fa notification +is +.Dv NULL +and the process is currently registered for notification by the specified +message queue, the existing registration will be removed. +.Pp +When the notification is sent to the registered process, its registration +is removed. +The message queue then is available for registration. +.Pp +If a process has registered for notification of message arrival at a +message queue and some thread is blocked in +.Fn mq_receive +waiting to receive a message when a message arrives at the queue, the +arriving message will satisfy the appropriate +.Fn mq_receive . +The resulting behavior is as if the message queue remains empty, and no +notification will be sent. +.Sh RETURN VALUES +.Rv -std +.Sh ERRORS +The +.Fn mq_notify +system call +will fail if: +.Bl -tag -width Er +.It Bq Er EBADF +The +.Fa mqdes +argument is not a valid message queue descriptor. +.It Bq Er EBUSY +Process is already registered for notification by the message queue. +.It Bq Er EINVAL +The asynchronous notification method in +.Fa notification->sigev_notify +is invalid or not supported. +.El +.Sh SEE ALSO +.Xr mq_open 2 , +.Xr mq_send 2 , +.Xr mq_timedsend 2 , +.Xr sigevent 3 , +.Xr siginfo 3 +.Sh STANDARDS +The +.Fn mq_notify +system call conforms to +.St -p1003.1-2004 . +.Sh HISTORY +Support for +.Tn POSIX +message queues first appeared in +.Fx 7.0 . +.Sh COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- +Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. In the +event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard is +the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html. |