NAME

lio_listio — list directed I/O (REALTIME)

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <aio.h>

int
lio_listio(int mode, struct aiocb * const list[], int nent, struct sigevent *sig);

DESCRIPTION

The lio_listio() function initiates a list of I/O requests with a single function call. The list argument is an array of pointers to aiocb structures describing each operation to perform, with nent elements. NULL elements are ignored.

The aio_lio_opcode field of each aiocb specifies the operation to be performed. The following operations are supported:

LIO_READ

Read data as if by a call to aio_read(2).

LIO_READV

Read data as if by a call to aio_readv(2).

LIO_NOP

No operation.

LIO_WRITE

Write data as if by a call to aio_write(2).

LIO_WRITEV

Write data as if by a call to aio_writev(2).

If the LIO_READ, LIO_READV, LIO_WRITE, LIO_WRITEV opcodes are or-ed with the LIO_FOFFSET flag, the corresponding read or write operation uses the current file descriptor offset instead of aio_offset from aiocb.

If the mode argument is LIO_WAIT, lio_listio() does not return until all the requested operations have been completed. If mode is LIO_NOWAIT, sig can be used to request asynchronous notification when all operations have completed. If sig is NULL, no notification is sent.

For SIGEV_KEVENT notifications, the posted kevent will contain:

For SIGEV_SIGNO and SIGEV_THREAD_ID notifications, the information for the queued signal will include SI_ASYNCIO in the si_code field and the value stored in sig->sigev_value in the si_value field.

For SIGEV_THREAD notifications, the value stored in sig->sigev_value is passed to the sig->sigev_notify_function as described in sigevent(3).

The order in which the requests are carried out is not specified; in particular, there is no guarantee that they will be executed in the order 0, 1, ..., nent-1.

RETURN VALUES

If mode is LIO_WAIT, the lio_listio() function returns 0 if the operations completed successfully, otherwise -1.

If mode is LIO_NOWAIT, the lio_listio() function returns 0 if the operations are successfully queued, otherwise -1.

ERRORS

The lio_listio() function will fail if:

[EAGAIN]

There are not enough resources to enqueue the requests.

[EAGAIN]

The request would cause the system-wide limit {AIO_MAX} to be exceeded.

[EINVAL]

The mode argument is neither LIO_WAIT nor LIO_NOWAIT, or nent is greater than {AIO_LISTIO_MAX}.

[EINVAL]

The asynchronous notification method in sig->sigev_notify is invalid or not supported.

[EINTR]

A signal interrupted the system call before it could be completed.

[EIO]

One or more requests failed.

In addition, the lio_listio() function may fail for any of the reasons listed for aio_read(2) and aio_write(2).

If lio_listio() succeeds, or fails with an error code of EAGAIN, EINTR, or EIO, some of the requests may have been initiated. The caller should check the error status of each aiocb structure individually by calling aio_error(2).

SEE ALSO

aio_error(2), aio_read(2), aio_readv(2), aio_write(2), aio_writev(2), read(2), write(2), sigevent(3), siginfo(3), aio(4)

STANDARDS

The lio_listio() function is expected to conform to IEEE Std 1003.1-2001 (“POSIX.1”). The LIO_READV and LIO_WRITEV operations are FreeBSD extensions, and should not be used in portable code.

HISTORY

The lio_listio() system call first appeared in FreeBSD 3.0.