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Message-ID: <1504159902.31031.11.camel@coelho.fi> (sfid-20170831_081204_250562_1E6AEBFA)
From: Luca Coelho <luca@coelho.fi>
To: David Weinehall <david.weinehall@linux.intel.com>
Cc: jikos@kernel.org, linux-wireless@vger.kernel.org,
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Date: Thu, 31 Aug 2017 09:11:42 +0300
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Subject: Re: [PATCH v2] iwlwifi: pcie: move rx workqueue initialization to
 iwl_trans_pcie_alloc()
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On Wed, 2017-08-30 at 17:57 +0300, David Weinehall wrote:
> On Tue, Aug 22, 2017 at 10:37:29AM +0300, Luca Coelho wrote:
> > From: Luca Coelho <luciano.coelho@intel.com>
> > 
> > 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>
> 
> With this patch I no longer get the lockdep warning,
> and the driver seems to work just as well as before.

Great! Thanks for reporting and testing, David!


> Thanks!
> 
> Tested-by: David Weinehall <david.weinehall@linux.intel.com>

Thanks for this too, but unfortunately it's too late to add it, since
the patch is already in net tree.

--
Cheers,
Luca.