freebsd/lib/libc/sys/lio_listio.2

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.Dd January 12, 2003
.Dt LIO_LISTIO 2
.Os
.Sh NAME
.Nm lio_listio
.Nd "list directed I/O (REALTIME)"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In aio.h
.Ft int
.Fo lio_listio
.Fa "int mode"
.Fa "struct aiocb * const list[]"
.Fa "int nent"
.Fa "struct sigevent *sig"
.Fc
.Sh DESCRIPTION
The
.Fn lio_listio
function initiates a list of I/O requests with a single function call.
The
.Fa list
argument is an array of pointers to
.Vt aiocb
structures describing each operation to perform,
with
.Fa nent
elements.
.Dv NULL
elements are ignored.
.Pp
The
.Va aio_lio_opcode
field of each
.Vt aiocb
specifies the operation to be performed.
The following operations are supported:
.Bl -tag -width ".Dv LIO_WRITE"
.It Dv LIO_READ
Read data as if by a call to
.Xr aio_read 2 .
.It Dv LIO_NOP
No operation.
.It Dv LIO_WRITE
Write data as if by a call to
.Xr aio_write 2 .
.El
.Pp
If the
.Fa mode
argument is
.Dv LIO_WAIT ,
.Fn lio_listio
does not return until all the requested operations have been completed.
If
.Fa mode
is
.Dv LIO_NOWAIT ,
the requests are processed asynchronously, and the signal specified by
.Fa sig
is sent when all operations have completed.
If
.Fa sig
is
.Dv NULL ,
the calling process is not notified of I/O completion.
.Pp
The order in which the requests are carried out is not specified;
in particular, there is no guarantee that they will be executed in
the order 0, 1, ...,
.Fa nent Ns \-1 .
.Sh RETURN VALUES
If
.Fa mode
is
.Dv LIO_WAIT ,
the
.Fn lio_listio
function returns 0 if the operations completed successfully,
otherwise \-1.
.Pp
If
.Fa mode
is
.Dv LIO_NOWAIT ,
the
.Fn lio_listio
function 0 if the operations are successfully queued,
otherwise \-1.
.Sh ERRORS
The
.Fn lio_listio
function will fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
There are not enough resources to enqueue the requests.
.It Bq Er EAGAIN
The request would cause the system-wide limit
.Dv AIO_MAX
to be exceeded.
.It Bq Er EINVAL
The
.Fa mode
argument is neither
.Dv LIO_WAIT
nor
.Dv LIO_NOWAIT ,
or
.Fa nent
is greater than
.Dv AIO_LISTIO_MAX .
.It Bq Er EINTR
A signal interrupted the system call before it could be completed.
.It Bq Er EIO
One or more requests failed.
.El
.Pp
In addition, the
.Fn lio_listio
function may fail for any of the reasons listed for
.Xr aio_read 2
and
.Xr aio_write 2 .
.Pp
If
.Fn lio_listio
succeeds, or fails with an error code of
.Er EAGAIN , EINTR ,
or
.Er EIO ,
some of the requests may have been initiated.
The caller should check the error status of each
.Vt aiocb
structure individually by calling
.Xr aio_error 2 .
.Sh SEE ALSO
.Xr aio_error 2 ,
.Xr aio_read 2 ,
.Xr aio_write 2 ,
.Xr read 2 ,
.Xr write 2 ,
.Xr siginfo 3 ,
.Xr aio 4
.Sh STANDARDS
The
.Fn lio_listio
function is expected to conform to
.St -p1003.1-2001 .