463970da7b
- Add a sigevent(3) manpage to give a general overview of the sigevent structure and the available notification mechanisms. - Document that AIO requests contain a nested sigevent structure that can be used to request completion notification. - Expand the sigevent details in other manuals to note details such as the extra values stored in a queued signal's information or in a posted kevent. Reviewed by: kib MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D7122
219 lines
4.7 KiB
Groff
219 lines
4.7 KiB
Groff
.\" Copyright (c) 2003 Tim J. Robbins
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 15, 2016
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.Dt LIO_LISTIO 2
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.Os
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.Sh NAME
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.Nm lio_listio
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.Nd "list directed I/O (REALTIME)"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In aio.h
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.Ft int
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.Fo lio_listio
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.Fa "int mode"
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.Fa "struct aiocb * const list[]"
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.Fa "int nent"
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.Fa "struct sigevent *sig"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn lio_listio
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function initiates a list of I/O requests with a single function call.
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The
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.Fa list
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argument is an array of pointers to
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.Vt aiocb
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structures describing each operation to perform,
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with
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.Fa nent
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elements.
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.Dv NULL
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elements are ignored.
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.Pp
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The
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.Va aio_lio_opcode
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field of each
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.Vt aiocb
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specifies the operation to be performed.
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The following operations are supported:
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.Bl -tag -width ".Dv LIO_WRITE"
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.It Dv LIO_READ
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Read data as if by a call to
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.Xr aio_read 2 .
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.It Dv LIO_NOP
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No operation.
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.It Dv LIO_WRITE
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Write data as if by a call to
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.Xr aio_write 2 .
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.El
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.Pp
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If the
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.Fa mode
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argument is
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.Dv LIO_WAIT ,
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.Fn lio_listio
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does not return until all the requested operations have been completed.
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If
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.Fa mode
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is
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.Dv LIO_NOWAIT ,
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.Fa sig
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can be used to request asynchronous notification when all operations have
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completed.
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If
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.Fa sig
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is
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.Dv NULL ,
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no notification is sent.
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.Pp
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For
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.Dv SIGEV_KEVENT
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notifications,
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the posted kevent will contain:
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.Bl -column ".Va filter"
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.It Sy Member Ta Sy Value
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.It Va ident Ta Fa list
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.It Va filter Ta Dv EVFILT_LIO
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.It Va udata Ta
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value stored in
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.Fa sig->sigev_value
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.El
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.Pp
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For
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.Dv SIGEV_SIGNO
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and
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.Dv SIGEV_THREAD_ID
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notifications,
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the information for the queued signal will include
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.Dv SI_ASYNCIO
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in the
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.Va si_code
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field and the value stored in
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.Fa sig->sigev_value
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in the
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.Va si_value
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field.
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.Pp
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For
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.Dv SIGEV_THREAD
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notifications,
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the value stored in
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.Fa sig->sigev_value
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is passed to the
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.Fa sig->sigev_notify_function
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as described in
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.Xr sigevent 3 .
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.Pp
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The order in which the requests are carried out is not specified;
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in particular, there is no guarantee that they will be executed in
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the order 0, 1, ...,
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.Fa nent Ns \-1 .
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.Sh RETURN VALUES
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If
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.Fa mode
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is
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.Dv LIO_WAIT ,
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the
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.Fn lio_listio
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function returns 0 if the operations completed successfully,
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otherwise \-1.
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.Pp
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If
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.Fa mode
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is
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.Dv LIO_NOWAIT ,
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the
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.Fn lio_listio
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function returns 0 if the operations are successfully queued,
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otherwise \-1.
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.Sh ERRORS
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The
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.Fn lio_listio
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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There are not enough resources to enqueue the requests.
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.It Bq Er EAGAIN
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The request would cause the system-wide limit
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.Dv AIO_MAX
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to be exceeded.
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.It Bq Er EINVAL
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The
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.Fa mode
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argument is neither
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.Dv LIO_WAIT
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nor
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.Dv LIO_NOWAIT ,
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or
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.Fa nent
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is greater than
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.Dv AIO_LISTIO_MAX .
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.It Bq Er EINVAL
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The asynchronous notification method in
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.Fa sig->sigev_notify
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is invalid or not supported.
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.It Bq Er EINTR
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A signal interrupted the system call before it could be completed.
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.It Bq Er EIO
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One or more requests failed.
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.El
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.Pp
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In addition, the
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.Fn lio_listio
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function may fail for any of the reasons listed for
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.Xr aio_read 2
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and
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.Xr aio_write 2 .
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.Pp
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If
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.Fn lio_listio
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succeeds, or fails with an error code of
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.Er EAGAIN , EINTR ,
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or
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.Er EIO ,
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some of the requests may have been initiated.
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The caller should check the error status of each
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.Vt aiocb
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structure individually by calling
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.Xr aio_error 2 .
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.Sh SEE ALSO
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.Xr aio_error 2 ,
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.Xr aio_read 2 ,
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.Xr aio_write 2 ,
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.Xr read 2 ,
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.Xr write 2 ,
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.Xr sigevent 3 ,
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.Xr siginfo 3 ,
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.Xr aio 4
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.Sh STANDARDS
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The
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.Fn lio_listio
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function is expected to conform to
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.St -p1003.1-2001 .
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