Re: [linuxwifi] x86/thermal: AB-BA dependency between mvm->mutex and tz->lock

From: Jiri Kosina
Date: Thu Aug 03 2017 - 07:34:32 EST

On Thu, 3 Aug 2017, Coelho, Luciano wrote:

> Okay, so as I understand it the problem has been there for a long time,
> but the splat is only coming up now because of Thomas' patch that adds
> the lockdep map[1], right?

Yeah, sorry, forgot to mention that pre-49dfe2a67797 kernels wouldn't
produce this, as there would not be aware of the fact that
cpus_read_lock() is actually semantically a lock.

> I see the workqueue allocation you mentioned. I'll try to move this
> allocation out of the mutex and see how it goes.

I have been briefly looking into this as well -- it'll basically have to
be moved out of the trans_pcie->mutex context, but

(a) I'm not sure whether that's actually safe
(b) iwl_pcie_rx_reuse_rbd() (which is where corresponding work is being
queued) is not a proper context either (it's atomic context)


Jiri Kosina