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@xxxxxxxxx>
> >
> > 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@xxxxxxxxx>
> > Reported-by: Jiri Kosina <jikos@xxxxxxxxxx>
> > Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
Thanks for this too, but unfortunately it's too late to add it, since
the patch is already in net tree.
--
Cheers,
Luca.
