From 53bdc88aac9a21aae937452724fa4738cd843795 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Wed, 24 Aug 2022 13:07:41 +0100 Subject: [PATCH] io_uring/notif: order notif vs send CQEs Currently, there is no ordering between notification CQEs and completions of the send flushing it, this quite complicates the userspace, especially since we don't flush notification when the send(+flush) request fails, i.e. there will be only one CQE. What we can do is to make sure that notification completions come only after sends. The easiest way to achieve this is to not try to complete a notification inline from io_sendzc() but defer it to task_work, considering that io-wq sendzc is disallowed CQEs will be naturally ordered because task_works will only be executed after we're done with submission and so inline completion. Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/cddfd1c2bf91f22b9fe08e13b7dffdd8f858a151.1661342812.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- io_uring/notif.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/io_uring/notif.c b/io_uring/notif.c index 568ff17dc552..96f076b175e0 100644 --- a/io_uring/notif.c +++ b/io_uring/notif.c @@ -81,8 +81,10 @@ void io_notif_slot_flush(struct io_notif_slot *slot) slot->notif = NULL; /* drop slot's master ref */ - if (refcount_dec_and_test(&nd->uarg.refcnt)) - io_notif_complete(notif); + if (refcount_dec_and_test(&nd->uarg.refcnt)) { + notif->io_task_work.func = __io_notif_complete_tw; + io_req_task_work_add(notif); + } } __cold int io_notif_unregister(struct io_ring_ctx *ctx) -- 2.34.1