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Add option for getting a completion without waiting

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This now exposes two helpers:

io_uring_get_completion()
	Return a completion, if we have one (or more) available in
	the ring

io_uring_wait_completion()
	Return a completion, waiting for it if necessary

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2019-01-08 15:14:07 -07:00
parent f93c84e1b0
commit 6a44c6e0f7
3 changed files with 28 additions and 9 deletions
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34
src/io_uring.c
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@@ -9,38 +9,54 @@
#include "liburing.h"
#include "barrier.h"
/*
* Return an IO completion, waiting for it it necessary.
*/
int io_uring_get_completion(int fd, struct io_uring_cq *cq,
struct io_uring_event **ev_ptr)
static int __io_uring_get_completion(int fd, struct io_uring_cq *cq,
struct io_uring_event **ev_ptr, int wait)
{
const unsigned mask = *cq->kring_mask;
struct io_uring_event *ev = NULL;
unsigned head;
int ret;
*ev_ptr = NULL;
head = *cq->khead;
do {
read_barrier();
if (head != *cq->ktail) {
ev = &cq->events[head & mask];
*ev_ptr = &cq->events[head & mask];
break;
}
if (!wait)
break;
ret = io_uring_enter(fd, 0, 1, IORING_ENTER_GETEVENTS);
if (ret < 0)
return -errno;
} while (1);
if (ev) {
if (*ev_ptr) {
*cq->khead = head + 1;
write_barrier();
}
*ev_ptr = ev;
return 0;
}
/*
* Return an IO completion, if one is readily available
*/
int io_uring_get_completion(int fd, struct io_uring_cq *cq,
struct io_uring_event **ev_ptr)
{
return __io_uring_get_completion(fd, cq, ev_ptr, 0);
}
/*
* Return an IO completion, waiting for it if necessary
*/
int io_uring_wait_completion(int fd, struct io_uring_cq *cq,
struct io_uring_event **ev_ptr)
{
return __io_uring_get_completion(fd, cq, ev_ptr, 1);
}
/*
* Submit iocbs acquired from io_uring_get_iocb() to the kernel.
*