io_setup(2)

1io_setup(2)                   System Calls Manual                  io_setup(2)
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NAME

6       io_setup - create an asynchronous I/O context
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LIBRARY

9       Standard C library (libc, -lc)
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11       Alternatively, Asynchronous I/O library (libaio, -laio); see VERSIONS.
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SYNOPSIS

14       #include <linux/aio_abi.h>          /* Defines needed types */
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16       long io_setup(unsigned int nr_events, aio_context_t *ctx_idp);
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18       Note: There is no glibc wrapper for this system call; see VERSIONS.
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DESCRIPTION

21       Note:  this  page  describes  the raw Linux system call interface.  The
22       wrapper function provided by libaio  uses  a  different  type  for  the
23       ctx_idp argument.  See VERSIONS.
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25       The io_setup() system call creates an asynchronous I/O context suitable
26       for concurrently processing nr_events operations.  The ctx_idp argument
27       must  not point to an AIO context that already exists, and must be ini‐
28       tialized to 0 prior to the call.  On successful  creation  of  the  AIO
29       context, *ctx_idp is filled in with the resulting handle.
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RETURN VALUE

32       On  success,  io_setup()  returns  0.  For the failure return, see VER‐
33       SIONS.
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ERRORS

36       EAGAIN The specified nr_events exceeds the limit of  available  events,
37              as defined in /proc/sys/fs/aio-max-nr (see proc(5)).
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39       EFAULT An invalid pointer is passed for ctx_idp.
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41       EINVAL ctx_idp  is  not initialized, or the specified nr_events exceeds
42              internal limits.  nr_events should be greater than 0.
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44       ENOMEM Insufficient kernel resources are available.
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46       ENOSYS io_setup() is not implemented on this architecture.
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VERSIONS

49       glibc does not provide a wrapper for this system call.  You  could  in‐
50       voke  it  using  syscall(2).  But instead, you probably want to use the
51       io_setup() wrapper function provided by libaio.
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53       Note that the libaio wrapper function uses a  different  type  (io_con‐
54       text_t *)  for the ctx_idp argument.  Note also that the libaio wrapper
55       does not follow the usual C library conventions for indicating  errors:
56       on  error it returns a negated error number (the negative of one of the
57       values  listed  in  ERRORS).   If  the  system  call  is  invoked   via
58       syscall(2), then the return value follows the usual conventions for in‐
59       dicating an error: -1, with errno set to a (positive) value that  indi‐
60       cates the error.
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STANDARDS

63       Linux.
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HISTORY

66       Linux 2.5.
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