io_getevents(3) Linux AIO io_getevents(3)

io_getevents, aio_pgetevents - Read resulting events from io requests

#include <errno.h>

#include <libaio.h>

struct iocb {
	void		*data;
	unsigned	key;
	short		aio_lio_opcode;
	short		aio_reqprio;
	int		aio_fildes;
};

struct io_event {

unsigned PADDED(data, __pad1);
unsigned PADDED(obj, __pad2);
unsigned PADDED(res, __pad3);
unsigned PADDED(res2, __pad4); }; int io_getevents(io_context_t ctx, long nr, struct io_event *events[], struct timespec *timeout); int io_pgetevents(io_context_t ctx, long nr, struct io_event *events[], struct timespec *timeout, sigset_t *sigmask);

Attempts to read up to nr events from the completion queue for the aio_context specified by ctx.

May return 0 if no events are available and the timeout specified by when has elapsed, where when == NULL specifies an infinite timeout. Note that the timeout pointed to by when is relative and will be updated if not NULL and the operation blocks. Will fail with ENOSYS if not implemented.

The relationship between io_getevents() and io_pgetevents() is analogous to the relationship between select(2) and pselect(2): similar to pselect(2), pgetevents() allows an application to safely wait until either an aio completion event happens or until a signal is caught.

The following io_pgetevents() call:


ret = io_pgetevents(ctx, min_nr, nr, events, timeout, sigmask);

is equivalent to atomically executing the following calls:


sigset_t origmask;
pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
ret = io_getevents(ctx, min_nr, nr, events, timeout);
pthread_sigmask(SIG_SETMASK, &origmask, NULL);

See the description of pselect(2) for an explanation of why io_pgetevents() is necessary.

If the sigmask argument is specified as NULL, then no signal mask manipulation is performed (and thus io_pgetevents() behaves the same as io_getevents()).

If ctx is invalid, if min_nr is out of range, if nr is out of range, if when is out of range.
If any of the memory specified to is invalid.

io(3), io_cancel(3), io_fsync(3), io_prep_fsync(3), io_prep_pread(3), io_prep_pwrite(3), io_queue_init(3), io_queue_release(3), io_queue_run(3), io_queue_wait(3), io_set_callback(3), io_submit(3), errno(3), pselect(2).

2019-07-23 Linux