io_setup(2)                   System Calls Manual                  io_setup(2)

NAME
       io_setup - create an asynchronous I/O context

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <linux/aio_abi.h>
       #include <sys/syscall.h>    /* Definition of SYS_* constants */
       #include <unistd.h>

       long syscall(SYS_io_setup, unsigned int n, aio_context_t *ctx_idp);

DESCRIPTION
       Note: you probably want to use the io_setup(3) wrapper function
       provided by libaio; see VERSIONS.

       The io_setup() system call creates an asynchronous I/O context suitable
       for concurrently processing n 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.  On error, -1 is returned, and errno
       is set to indicate the error.

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

       EFAULT An invalid pointer is passed for ctx_idp.

       EINVAL *ctx_idp is not initialized to 0.

       EINVAL The specified n exceeds internal limits.  n should be greater
              than 0.

       ENOMEM Insufficient kernel resources are available.

       ENOSYS io_setup() is not implemented on this architecture.

VERSIONS
       libaio <https://pagure.io/libaio> provides a wrapper function with the
       same name, but different prototype and return value.  You probably want
       to use that wrapper.

STANDARDS
       Linux.

HISTORY
       Linux 2.5.

SEE ALSO
       io_cancel(2), io_destroy(2), io_getevents(2), io_submit(2),
       io_setup(3), aio(7)

Linux man-pages 6.19              2026-04-11                       io_setup(2)