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io_uring/napi: don't busy poll past an expired timeout

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__io_napi_busy_loop() caps the busy poll time to what is left until the
timeout of the wait. The difference is negative if the timeout has passed
already, which is what an application gets if it uses
IORING_ENTER_ABS_TIMER with a time that isn't in the future any more. The
min_t(u64, ...) turns that into a huge value, so the cap has no effect
and the wait, which should return right away, spins for the full busy
poll time first.

Fixes: d5cce407e4 ("io_uring/napi: postpone napi timeout adjustment")
Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-34-c1556f5d7bf5@toxicpanda.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Josef Bacik 2026-10-15 19:30:58 +00:00 committed by Jens Axboe
parent 9c15164878
commit 21ed976c12
1 changed files with 2 additions and 0 deletions
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2
io_uring/napi.c
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@ -378,6 +378,8 @@ void __io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq)
if (iowq->timeout != KTIME_MAX) {
ktime_t dt = ktime_sub(iowq->timeout, io_get_time(ctx));
/* an absolute timeout may have passed already */
dt = max_t(ktime_t, dt, 0);
iowq->napi_busy_poll_dt = min_t(u64, iowq->napi_busy_poll_dt, dt);
}