From 74a37ce697f3fa393324990c872a3a8933344f64 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Mon, 9 Jan 2023 14:46:10 +0000 Subject: [PATCH] io_uring: fix waiters missing wake ups There are reports of mariadb hangs, which is caused by a missing barrier in the waking code resulting in waiters losing events. The problem was introduced in a backport 3ab9326f93ec4 ("io_uring: wake up optimisations"), and the change restores the barrier present in the original commit 3ab9326f93ec4 ("io_uring: wake up optimisations") Reported by: Xan Charbonnet Fixes: 3ab9326f93ec4 ("io_uring: wake up optimisations") Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1093243#99 Reviewed-by: Li Zetao Signed-off-by: Pavel Begunkov Signed-off-by: Greg Kroah-Hartman --- io_uring/io_uring.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 480752fc3eb6..64502323be5e 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -597,8 +597,10 @@ static inline void __io_cq_unlock_post_flush(struct io_ring_ctx *ctx) io_commit_cqring(ctx); spin_unlock(&ctx->completion_lock); io_commit_cqring_flush(ctx); - if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) + if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) { + smp_mb(); __io_cqring_wake(ctx); + } } void io_cq_unlock_post(struct io_ring_ctx *ctx)