Re: [PATCH 5.13 000/800] 5.13.2-rc1 review

[Jan Kara]

On Wed 14-07-21 16:26:52, Greg Kroah-Hartman wrote:
> On Wed, Jul 14, 2021 at 07:29:26PM +0530, Naresh Kamboju wrote:
> > On Wed, 14 Jul 2021 at 19:22, Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> wrote:
> > >
> > > On Wed, 14 Jul 2021 at 19:01, Greg Kroah-Hartman
> > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > >
> > 
> > <trim>
> > 
> > > My two cents,
> > > While running ssuite long running stress testing we have noticed deadlock.
> > >
> > > > So if you drop that, all works well?  I'll go drop that from the queues
> > > > now.
> > >
> > > Let me drop that patch and test it again.
> > >
> > > Crash log,
> > >
> > > [ 1957.278399] ============================================
> > > [ 1957.283717] WARNING: possible recursive locking detected
> > > [ 1957.289031] 5.13.2-rc1 #1 Not tainted
> > > [ 1957.292703] --------------------------------------------
> > > [ 1957.298016] kworker/u8:7/236 is trying to acquire lock:
> > > [ 1957.303241] ffff8cc203f92c38 (&bfqd->lock){-.-.}-{2:2}, at:
> > > bfq_finish_requeue_request+0x55/0x500 [bfq]
> > > [ 1957.312643]
> > > [ 1957.312643] but task is already holding lock:
> > > [ 1957.318467] ffff8cc203f92c38 (&bfqd->lock){-.-.}-{2:2}, at:
> > > bfq_insert_requests+0x81/0x1750 [bfq]
> > > [ 1957.327334]
> > > [ 1957.327334] other info that might help us debug this:
> > > [ 1957.333852]  Possible unsafe locking scenario:
> > > [ 1957.333852]
> > > [ 1957.339762]        CPU0
> > > [ 1957.342206]        ----
> > > [ 1957.344651]   lock(&bfqd->lock);
> > > [ 1957.347873]   lock(&bfqd->lock);
> > > [ 1957.351097]
> > > [ 1957.351097]  *** DEADLOCK ***
> > > [ 1957.351097]
> > 
> > Also noticed on stable-rc 5.12.17-rc1.
> 
> I dropped the same patch from there as well already, thanks.

OK, when you dropped this patch, please also drop upstream commit
fd2ef39cc9a6b ("blk: Fix lock inversion between ioc lock and bfqd lock").
Because without BFQ patch this block layer patch could cause some
use-after-free issues. I'll have a look if I can understand why BFQ patch
causes problems in stable kernels...

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR