io_setup(2)

NAME
io_setup - create an asynchronous I/O context

LIBRARY
Standard C library (libc, -lc)

Alternatively, Asynchronous I/O library (libaio, -laio); see NOTES.

SYNOPSIS
#include <linux/aio_abi.h>          /* Defines needed types */

long io_setup(unsigned int nr_events, aio_context_t *ctx_idp);

Note: There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION
Note: this page describes the raw Linux system call interface. The wrapper function provided by libaio uses a different type for the ctx_idp argument. See NOTES.

The io_setup() system call creates an asynchronous I/O context suitable for concurrently processing nr_events operations. The ctx_idp argument must not point to an AIO context that already exists, and must be initialized to 0 prior to the call. On successful creation of the AIO context, *ctx_idp is filled in with the resulting handle.

RETURN VALUE
On success, io_setup() returns 0. For the failure return, see NOTES.

ERRORS

EAGAIN
    The specified nr_events exceeds the limit of available events, as defined in /proc/sys/fs/aio-max-nr (see proc(5)).

EFAULT
    An invalid pointer is passed for ctx_idp.

EINVAL
    ctx_idp is not initialized, or the specified nr_events exceeds internal limits. nr_events should be greater than 0.

ENOMEM
    Insufficient kernel resources are available.

ENOSYS
    io_setup() is not implemented on this architecture.

VERSIONS
The asynchronous I/O system calls first appeared in Linux 2.5.

STANDARDS
io_setup() is Linux-specific and should not be used in programs that are intended to be portable.

NOTES
Glibc does not provide a wrapper for this system call. You could invoke it using syscall(2). But instead, you probably want to use the io_setup() wrapper function provided by libaio.

Note that the libaio wrapper function uses a different type (io_context_t *) for the ctx_idp argument. Note also that the libaio wrapper does not follow the usual C library conventions for indicating errors: on error it returns a negated error number (the negative of one of the values listed in ERRORS). If the system call is invoked via syscall(2), then the return value follows the usual conventions for indicating an error: -1, with errno set to a (positive) value that indicates the error.

SEE ALSO
io_cancel(2), io_destroy(2), io_getevents(2), io_submit(2), aio(7)