io_cqring_wait() doesn't run normal task_work after the local work, and it's the only location to do it in that order. Normally this doesn't matter, except if: 1) The ring is setup with DEFER_TASKRUN 2) The local work item may generate normal task_work For condition 2, this can happen when closing a file and it's the final put of that file, for example. This can cause stalls where a task is waiting to make progress, but there's nothing else that will wake it up. Link: https://github.com/axboe/liburing/issues/1235 Cc: stable@xxxxxxxxxxxxxxx Fixes: 846072f16eed ("io_uring: mimimise io_cqring_wait_schedule") Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 1aca501efaf6..d6a2cd351525 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2568,9 +2568,9 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags, * If we got woken because of task_work being processed, run it * now rather than let the caller do another wait loop. */ - io_run_task_work(); if (!llist_empty(&ctx->work_llist)) io_run_local_work(ctx, nr_wait); + io_run_task_work(); /* * Non-local task_work will be run on exit to userspace, but -- Jens Axboe
