[ 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@xxxxxxxxxxxxxx>
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@xxxxxxxxx>
---
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)
--
2.47.1
