linux-kernel - Re: [PATCH 00/23] interconnect: fix racy provider registration

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Date:   Thu, 2 Feb 2023 13:20:36 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Georgi Djakov <djakov@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Artur Świgoń <a.swigon@...sung.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/23] interconnect: fix racy provider registration

On Thu, Feb 02, 2023 at 12:13:33PM +0100, Krzysztof Kozlowski wrote:
> On 01/02/2023 11:15, Johan Hovold wrote:
> > The current interconnect provider interface is inherently racy as
> > providers are expected to be registered before being fully initialised.
> > 
> > This can specifically cause racing DT lookups to fail as I recently
> > noticed when the Qualcomm cpufreq driver failed to probe:
> > 
> > 	of_icc_xlate_onecell: invalid index 0
> >         cpu cpu0: error -EINVAL: error finding src node
> >         cpu cpu0: dev_pm_opp_of_find_icc_paths: Unable to get path0: -22
> >         qcom-cpufreq-hw: probe of 18591000.cpufreq failed with error -22
> > 
> > This only happens very rarely, but the bug is easily reproduced by
> > increasing the race window by adding an msleep() after registering
> > osm-l3 interconnect provider.
> > 
> > Note that the Qualcomm cpufreq driver is especially susceptible to this
> > race as the interconnect path is looked up from the CPU nodes so that
> > driver core does not guarantee the probe order even when device links
> > are enabled (which they not always are).
> > 
> > This series adds a new interconnect provider registration API which is
> > used to fix up the interconnect drivers before removing the old racy
> > API.
> > 
> 
> So is there a dependency or not? Can you make it clear that I shouldn't
> take memory controller bits?

As the fixes depend on the new API it is best if these could all go
through Georgi's tree.

Johan