[ upstream commit 3181e22fb79910c7071e84a43af93ac89e8a7106 ]
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 xan@charbonnet.com Fixes: 3ab9326f93ec4 ("io_uring: wake up optimisations") Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1093243#99 Signed-off-by: Pavel Begunkov asml.silence@gmail.com --- 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 9b58ba4616d40..e5a8ee944ef59 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -592,8 +592,10 @@ 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)