6.1-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
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 Reviewed-by: Li Zetao lizetao1@huawei.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -597,8 +597,10 @@ static inline void __io_cq_unlock_post_f 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)