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

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Date:   Thu, 3 Aug 2017 15:09:29 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     "Coelho, Luciano" <luciano.coelho@...el.com>
cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linuxwifi <linuxwifi@...el.com>,
        "Zhang, Rui" <rui.zhang@...el.com>,
        "edubezval@...il.com" <edubezval@...il.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "Weinehall, David" <david.weinehall@...el.com>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "Sharon, Sara" <sara.sharon@...el.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
Subject: Re: [linuxwifi] x86/thermal: AB-BA dependency between mvm->mutex
 and tz->lock

On Thu, 3 Aug 2017, Jiri Kosina wrote:

> > 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)

Actually moving it out of trans_pcie->mutex is likely not to be enough, 
the dependency would still be there, just the graph will have one vertex 
less, with the dependency going directly from mvm mutex to 
cpu_hotplug_lock.

-- 
Jiri Kosina
SUSE Labs