mirror of https://github.com/mkerrisk/man-pages
112 lines
2.8 KiB
Groff
112 lines
2.8 KiB
Groff
.\" Copyright (C) 2003 Free Software Foundation, Inc.
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.\"
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.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
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.\" This file is distributed according to the GNU General Public License.
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.\" %%%LICENSE_END
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.\"
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.TH IO_SETUP 2 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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io_setup \- create an asynchronous I/O context
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.SH SYNOPSIS
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.nf
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.BR "#include <linux/aio_abi.h>" " /* Defines needed types */"
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.PP
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.BI "long io_setup(unsigned int " nr_events ", aio_context_t *" ctx_idp );
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.fi
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.PP
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.IR Note :
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There is no glibc wrapper for this system call; see NOTES.
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.SH DESCRIPTION
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.IR Note :
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this page describes the raw Linux system call interface.
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The wrapper function provided by
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.I libaio
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uses a different type for the
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.I ctx_idp
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argument.
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See NOTES.
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.PP
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The
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.BR io_setup ()
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system call
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creates an asynchronous I/O context suitable for concurrently processing
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\fInr_events\fP operations.
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The
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.I ctx_idp
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argument must not point to an AIO context that already exists, and must
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be initialized to 0 prior to the call.
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On successful creation of the AIO context, \fI*ctx_idp\fP is filled in
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with the resulting handle.
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.SH RETURN VALUE
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On success,
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.BR io_setup ()
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returns 0.
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For the failure return, see NOTES.
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.SH ERRORS
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.TP
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.B EAGAIN
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The specified \fInr_events\fP exceeds the limit of available events,
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as defined in
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.IR /proc/sys/fs/aio\-max\-nr
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(see
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.BR proc (5)).
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.TP
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.B EFAULT
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An invalid pointer is passed for \fIctx_idp\fP.
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.TP
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.B EINVAL
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\fIctx_idp\fP is not initialized, or the specified \fInr_events\fP
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exceeds internal limits.
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\fInr_events\fP should be greater than 0.
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.TP
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.B ENOMEM
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Insufficient kernel resources are available.
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.TP
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.B ENOSYS
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.BR io_setup ()
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is not implemented on this architecture.
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.SH VERSIONS
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The asynchronous I/O system calls first appeared in Linux 2.5.
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.SH CONFORMING TO
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.BR io_setup ()
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is Linux-specific and should not be used in programs
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that are intended to be portable.
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.SH NOTES
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Glibc does not provide a wrapper for this system call.
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You could invoke it using
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.BR syscall (2).
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But instead, you probably want to use the
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.BR io_setup ()
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wrapper function provided by
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.\" http://git.fedorahosted.org/git/?p=libaio.git
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.IR libaio .
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.PP
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Note that the
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.I libaio
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wrapper function uses a different type
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.RI ( "io_context_t\ *" )
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.\" But glibc is confused, since <libaio.h> uses 'io_context_t' to declare
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.\" the system call.
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for the
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.I ctx_idp
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argument.
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Note also that the
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.I libaio
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wrapper does not follow the usual C library conventions for indicating errors:
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on error it returns a negated error number
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(the negative of one of the values listed in ERRORS).
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If the system call is invoked via
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.BR syscall (2),
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then the return value follows the usual conventions for
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indicating an error: \-1, with
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.I errno
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set to a (positive) value that indicates the error.
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.SH SEE ALSO
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.BR io_cancel (2),
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.BR io_destroy (2),
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.BR io_getevents (2),
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.BR io_submit (2),
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.BR aio (7)
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.\" .SH AUTHOR
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.\" Kent Yoder.
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