linux-kernel - Re: [PATCH v2] iwlwifi: pcie: move rx workqueue initialization to iwl_trans_pcie

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Date:   Thu, 31 Aug 2017 09:11:42 +0300
From:   Luca Coelho <luca@...lho.fi>
To:     David Weinehall <david.weinehall@...ux.intel.com>
Cc:     jikos@...nel.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxwifi@...el.com,
        rui.zhang@...el.com, edubezval@...il.com, linux-pm@...r.kernel.org,
        david.weinehall@...el.com, johannes.berg@...el.com,
        kvalo@...eaurora.org, sara.sharon@...el.com,
        emmanuel.grumbach@...el.com
Subject: Re: [PATCH v2] iwlwifi: pcie: move rx workqueue initialization to
 iwl_trans_pcie_alloc()

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@...el.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@...el.com>
> > Reported-by: Jiri Kosina <jikos@...nel.org>
> > Signed-off-by: Luca Coelho <luciano.coelho@...el.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@...ux.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.