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:

quoted

From: Luca Coelho <redacted>

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 <redacted>
Reported-by: Jiri Kosina <jikos@kernel.org>
Signed-off-by: Luca Coelho <redacted>

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 <redacted>

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

--
Cheers,
Luca.