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src/queue: don't wait twice if looping in _io_uring_get_cqe()

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If the caller asks for > 1 events with a timeout and we get just 1 event,
then we end up looping around and issuing an IORING_ENTER_GETEVENTS
with the timeout set twice. This results in twice the timeout that the
caller asked for.

Add a ->has_ts argument to struct get_data and don't re-enter if we've
already looped and it is set.

Also be a bit saner in not overwriting the return value, if set, and
return the initial value from io_uring_enter().

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2022-10-21 13:55:37 -07:00
parent dc73e72c4e
commit 40cbfe3db2
1 changed files with 24 additions and 6 deletions
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src/queue.c
+24 -6
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@@ -55,6 +55,7 @@ struct get_data {
unsigned wait_nr;
unsigned get_flags;
int sz;
int has_ts;
void *arg;
};
@@ -64,7 +65,7 @@ static int _io_uring_get_cqe(struct io_uring *ring,
{
struct io_uring_cqe *cqe = NULL;
bool looped = false;
int err;
int err = 0;
do {
bool need_enter = false;
@@ -72,9 +73,12 @@ static int _io_uring_get_cqe(struct io_uring *ring,
unsigned nr_available;
int ret;
err = __io_uring_peek_cqe(ring, &cqe, &nr_available);
if (err)
ret = __io_uring_peek_cqe(ring, &cqe, &nr_available);
if (ret) {
if (!err)
err = ret;
break;
}
if (!cqe && !data->wait_nr && !data->submit) {
/*
* If we already looped once, we already entererd
@@ -82,7 +86,8 @@ static int _io_uring_get_cqe(struct io_uring *ring,
* wait for, don't keep retrying.
*/
if (looped || !cq_ring_needs_enter(ring)) {
err = -EAGAIN;
if (!err)
err = -EAGAIN;
break;
}
need_enter = true;
@@ -95,6 +100,13 @@ static int _io_uring_get_cqe(struct io_uring *ring,
need_enter = true;
if (!need_enter)
break;
if (looped && data->has_ts) {
struct io_uring_getevents_arg *arg = data->arg;
if (!cqe && arg->ts && !err)
err = -ETIME;
break;
}
if (ring->int_flags & INT_FLAG_REG_RING)
flags |= IORING_ENTER_REGISTERED_RING;
@@ -102,14 +114,18 @@ static int _io_uring_get_cqe(struct io_uring *ring,
data->wait_nr, flags, data->arg,
data->sz);
if (ret < 0) {
err = ret;
if (!err)
err = ret;
break;
}
data->submit -= ret;
if (cqe)
break;
looped = true;
if (!looped) {
looped = true;
err = ret;
}
} while (1);
*cqe_ptr = cqe;
@@ -233,6 +249,7 @@ static int io_uring_wait_cqes_new(struct io_uring *ring,
.wait_nr = wait_nr,
.get_flags = IORING_ENTER_EXT_ARG,
.sz = sizeof(arg),
.has_ts = ts != NULL,
.arg = &arg
};
@@ -317,6 +334,7 @@ int io_uring_submit_and_wait_timeout(struct io_uring *ring,
.wait_nr = wait_nr,
.get_flags = IORING_ENTER_EXT_ARG,
.sz = sizeof(arg),
.has_ts = ts != NULL,
.arg = &arg
};