linux-kernel - Re: LOCKDEP warning due to ext_devt

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Message-ID: <20150528134511.27f9bdbc@notabene.brown>
Date:	Thu, 28 May 2015 13:45:11 +1000
From:	NeilBrown <neilb@...e.de>
To:	Jens Axboe <axboe@...com>
Cc:	Keith Busch <keith.busch@...el.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: LOCKDEP warning due to ext_devt_lock

On Wed, 27 May 2015 21:32:21 -0600 Jens Axboe <axboe@...com> wrote:

> On 05/27/2015 08:32 PM, NeilBrown wrote:
> >
> > Hi Keith,
> >   I'm getting lockdep warning around use of ext_devt_lock.
> >
> > [11428.266019] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
> >
> >   As you say in
> >      2da78092dda1 ("block: Fix dev_t minor allocation lifetime")
> > ext_devt_lock can be taken from call_rcu's soft-irq.
> > I think that means it should always use the _irq verion of spinlock.
> 
> Wouldn't spin_lock_bh() and friends suffice then?
> 

Quite possibly.  I've never actually used those so I don't tend to think
about them.  But only reflection I think they would be exactly right.
I'll modify my patch for future testing.

BTW, did you get my:

   [PATCH v2] block: discard bdi_unregister() in favour of bdi_destroy()

??  I haven't seen it appear in your 'block' tree.

Thanks,
NeilBrown

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