IO_SETUP(2)                         Linux Programmer's Manual                         IO_SETUP(2)



NAME
       io_setup - create an asynchronous I/O context

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

       int io_setup(unsigned nr_events, aio_context_t *ctx_idp);

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

DESCRIPTION
       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 cre‐
       ation 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 user's limit of available events, as defined in
              /proc/sys/fs/aio-max-nr.

       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.

CONFORMING TO
       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 function for this system call.  You could invoke it using
       syscall(2).  But instead, you probably want to use the io_setup()  wrapper  function  pro‐
       vided 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 nega‐
       tive 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)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2013-06-21                                IO_SETUP(2)