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From: Luca Coelho <luca@coelho.fi>
To: Jiri Kosina <jikos@kernel.org>
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Date: Thu, 24 Aug 2017 23:00:18 +0300
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Subject: Re: [PATCH v2] iwlwifi: pcie: move rx workqueue initialization to
 iwl_trans_pcie_alloc()
Sender: linux-wireless-owner@vger.kernel.org
List-ID: <linux-wireless.vger.kernel.org>

On Thu, 2017-08-24 at 21:56 +0200, Jiri Kosina wrote:
> On Thu, 24 Aug 2017, Luca Coelho wrote:
> 
> > > Work queues cannot be allocated when a mutex is held because the mutex
> > > may be in use and that would make it sleep.  Doing so generates the
> > > following splat with 4.13+:
> > > 
> > > [   19.513298] ======================================================
> > > [   19.513429] WARNING: possible circular locking dependency detected
> > > [   19.513557] 4.13.0-rc5+ #6 Not tainted
> > > [   19.513638] ------------------------------------------------------
> > > [   19.513767] cpuhp/0/12 is trying to acquire lock:
> > > [   19.513867]  (&tz->lock){+.+.+.}, at: [<ffffffff924afebb>] thermal_zone_get_temp+0x5b/0xb0
> > > [   19.514047]
> > > [   19.514047] but task is already holding lock:
> > > [   19.514166]  (cpuhp_state){+.+.+.}, at: [<ffffffff91cc4baa>] cpuhp_thread_fun+0x3a/0x210
> > > [   19.514338]
> > > [   19.514338] which lock already depends on the new lock.
> > > 
> > > This lock dependency already existed with previous kernel versions,
> > > but it was not detected until commit 49dfe2a67797 ("cpuhotplug: Link
> > > lock stacks for hotplug callbacks") was introduced.
> > > 
> > > Reported-by: David Weinehall <david.weinehall@intel.com>
> > > Reported-by: Jiri Kosina <jikos@kernel.org>
> > > Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
> > 
> > Jiri, did you have a chance to try this out? I'm about to ask Kalle to
> > merge this so it gets in in time for 4.13-rc7.
> 
> Sorry, I am almost completely offline for one more week (vacation), and 
> will not have access to the affected system before that.

Sounds good! Enjoy! ;)


>  But this indeed 
> looks like a correct fix to me, so feel free to add
> 
> 	Acked-by: Jiri Kosina <jkosina@suse.cz>
> 
> I'll be able to provide my Tested-by: eventually only in ~10 days.


Kalle already picked it up in wireless-drivers and this should make it's
way to 4.13-rc7 (we hope).

In any case, thanks for reporting and the help debugging it.

--
Cheers,
Luca.