Re: [PATCH stable-6.1 1/1] io_uring: fix waiters missing wake ups

[Greg KH <greg@kroah.com>]

On Sat, Jan 25, 2025 at 06:59:06AM +0000, lizetao wrote:
> 
> 
> > -----Original Message-----
> > From: Pavel Begunkov <asml.silence@gmail.com>
> > Sent: Saturday, January 25, 2025 2:54 AM
> > To: io-uring@vger.kernel.org; stable@vger.kernel.org
> > Cc: asml.silence@gmail.com; Xan Charbonnet <xan@charbonnet.com>;
> > Salvatore Bonaccorso <carnil@debian.org>
> > Subject: [PATCH stable-6.1 1/1] io_uring: fix waiters missing wake ups
> > 
> > [ 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)
> > --
> > 2.47.1
> > 
> 
> Reviewed-by: Li Zetao <lizetao1@huawei.com>

Now queued up, thanks.

greg k-h