linux-kernel - Re: [PATCH v6 46/52] opp: Put interconnect paths outside of opp_table

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Message-ID: <20201028040320.4nobxzudy3fuwmms@vireshk-i7>
Date:   Wed, 28 Oct 2020 09:33:20 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Mikko Perttunen <cyndis@...si.fi>,
        Viresh Kumar <vireshk@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v6 46/52] opp: Put interconnect paths outside of
 opp_table_lock

On 27-10-20, 23:26, Dmitry Osipenko wrote:
> 27.10.2020 08:10, Viresh Kumar пишет:
> > On 26-10-20, 01:17, Dmitry Osipenko wrote:
> >> This patch fixes lockup which happens when OPP table is released if
> >> interconnect provider uses OPP in the icc_provider->set() callback
> >> and bandwidth of the ICC path is set to 0 by the ICC core when path
> >> is released. The icc_put() doesn't need the opp_table_lock protection,
> >> hence let's move it outside of the lock in order to resolve the problem.
> >>
> >> In particular this fixes tegra-devfreq driver lockup on trying to unload
> >> the driver module. The devfreq driver uses OPP-bandwidth API and its ICC
> >> provider also uses OPP for DVFS, hence they both take same opp_table_lock
> >> when OPP table of the devfreq is released.
> >>
> >> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> >> ---
> ...
> > 
> > Never make such _fixes_ part of such a big patchset. Always send them
> > separately.
> 
> Perhaps it's not obvious from the commit description that this patch
> doesn't fix any known problems of the current mainline kernel and it's
> needed only for the new patches.

No, I understood that we started getting the warning now only after
some other patches of yours. Nevertheless, it should be considered as
a fix only as that generated lockdep because of locking placement. And
so sending such stuff separately is better as that allows people to
apply it fast.

> > Having said that, I already have a patch with me which shall fix it for you as
> > well:
> 
> I see that yours fix is already applied, thanks!

I hope it worked for you. Thanks.

-- 
viresh