Manpages - io_setup.2

io_setup - create an asynchronous I/O context

  #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.

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.

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

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.

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

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

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.

*io_cancel*(2), *io_destroy*(2), *io_getevents*(2), *io_submit*(2), *aio*(7)

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