lio_listio - Initiates a list of asynchronous I/O requests
#include <aio.h>
int lio_listio (
int mode,
struct aiocb *list,
int nent,
struct sigevent *sig );
Asynchronous I/O Library (libaio, libaio_raw)
Determines whether the lio_listio function returns when
the I/O operations are completed or as soon as the operations
are queued. The mode argument can have a value of
either LIO_WAIT or LIO_NOWAIT. Specifies a pointer to an
array of pointers to aiocb structures. The array contains
nent elements. Specifies the length of the array pointed
to by the list argument. The nent argument also specifies
the number of I/O operations potentially performed by the
lio_listio function. Specifies a pointer to a sigevent
structure.
The lio_listio function allows the calling process to initiate
a list of I/O requests with a single function call.
The mode argument determines whether the function returns
after the I/O operations are complete or as soon as they
have been queued.
The list argument is a pointer to an array of pointers to
aiocb structures. The aio_lio_opcode field of each aiocb
structure specifies the operation to be performed and can
take any one of three values; LIO_READ, LIO_WRITE, and
LIO_NOP as defined in the <aio.h> header file. Whether the
operation is specified as a read or write operation, the
list array element contains the address of the aiocb
structure for that operation. If the list array element is
NULL, that array element will be skipped. If the
aio_lio_opcode is LIO_READ, the I/O operation is submitted
as an aio_read operation. If the aio_lio_opcode is
LIO_WRITE, the I/O operation is submitted as an aio_write
operation. If the aio_lio_opcode is LIO_NOP, the list
entry is skipped.
The aio_fildes member of the aiocb structure specifies the
file descriptor for the operation. The aio_buf member
specifies the address of the data transfer buffer. The
number of bytes to be transferred is specified in the
aio_nbytes member.
The sig argument points to a sigevent structure, which
contains the signal number of the signal to be sent upon
completion of the asynchronous I/O operation. If you specify
LIO_WAIT, the function waits until all I/O operations
are completed, and the sig argument is ignored. If you
specify LIO_NOWAIT, and the sigev_notify element of the
sigevent structure equals SIGEV_SIGNAL and sigev_signo
does not equal 0 (zero), the signal is generated.
If the mode argument has the value LIO_NOWAIT, the
lio_listio function returns the value 0 (zero) if the I/O
operations are successfully queued. Otherwise, the function
returns -1 and sets errno to indicate the error type.
If the mode argument has the value LIO_WAIT, the lio_listio
function returns the value 0 (zero) when all the indicated
I/O operations complete successfully. Otherwise, the
function returns -1 and sets errno to indicate the error
type.
In either case, the return value indicates only the success
or failure of the lio_listio function call, not the
status of individual I/O requests. In some cases, one or
more of the I/O requests contained in the list may fail.
Failure of an individual request does not prevent completion
of any other individual request. To determine the
outcome of each I/O request, examine the error status
associated with each lio_aiocb control block. These error
statuses are identical to those returned as the result of
an aio_read or aio_write function.
The address of the aiocb structure is used as a handle for
retrieving the error and return status of the asynchronous
operation while it is in progress (equal to [EINPROGRESS]).
The error codes returned are identical to
those returned as the result of an aio_read or aio_write
function.
If an error occurs, the only way to determine which operations
were initiated is to check the aiocb by using the
aio_error function.
The lio_listio function fails under the following conditions:
The resources necessary to queue all the I/O
requests were not available. The application may check
the error status for each aiocb to determine the individual
requests that failed. The number of entries indicated
by nent would exceed the system limit of AIO_MAX. A signal
or event was delivered while waiting for all I/O
requests to complete during a LIO_WAIT operation. Each I/O
operation invoked by the lio_listio function may send a
signal when it completes. Therefore, this error may be
caused by the completion of one or more of the very operations
being awaited. Outstanding I/O requests are not canceled,
and the application must examine each list element
to determine whether the request was initiated, interrupted,
or completed. One or more of the individual I/O
operations failed. The application may check error status
for each aiocb structure to determine the individual
requests that failed. The mode argument is not a proper
value. Nent was greater than AIO_LISTIO_MAX. aio_lio
opcode is invalid.
If the aio_listio function succeeds or fails with errors
of [EAGAIN], [EINTR], or [EIO], then some of the I/O specified
by the list may have been initiated. The I/O operation
indicated by each list element can encounter errors
specific to the individual read or write function being
performed. In this event, the error status for each aiocb
control block contains the asociated error code. These
error codes are the same as for a call to the read or
write function. One of the following additional errors may
occur: The requested I/O operation was not queued due to
resource limitations. The requested I/O operation was
canceled by aio_cancel. The requested I/O is in progress.
Functions: close(2), exec(2), _exit(2), fork(2), lseek(2),
read(2), write(2), aio_cancel(3), aio_error(3),
aio_group_completion_np(3), aio_read(3),
aio_results_np(3), aio_return(3), aio_write(3)
Guide to Realtime Programming
lio_listio(3)
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