IO_CANCEL

Section: Linux Programmer's Manual (2)
Updated: 2020-12-21
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NAME

io_cancel - cancel an outstanding asynchronous I/O operation

SYNOPSIS

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

int io_cancel(aio_context_t ctx_id, struct iocb *iocb,
              struct io_event *result);

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_id argument. See NOTES.

The io_cancel() system call attempts to cancel an asynchronous I/O operation previously submitted with io_submit(2). The iocb argument describes the operation to be canceled and the ctx_id argument is the AIO context to which the operation was submitted. If the operation is successfully canceled, the event will be copied into the memory pointed to by result without being placed into the completion queue.

RETURN VALUE

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

ERRORS

EAGAIN: The iocb specified was not canceled.
EFAULT: One of the data structures points to invalid data.
EINVAL: The AIO context specified by ctx_id is invalid.
ENOSYS: io_cancel() is not implemented on this architecture.

VERSIONS

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

CONFORMING TO

io_cancel() 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_cancel() wrapper function provided by libaio.

Note that the libaio wrapper function uses a different type (io_context_t) for the ctx_id 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.

COLOPHON

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