Message-ID: <57dbcbc6-b497-53db-5a45-abce0e4dcf37@linaro.org>
Date:   Thu, 2 Feb 2023 12:13:33 +0100
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Subject: Re: [PATCH 00/23] interconnect: fix racy provider registration
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To:     Johan Hovold <johan+linaro@kernel.org>,
        Georgi Djakov <djakov@kernel.org>
Cc:     Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Sylwester Nawrocki <s.nawrocki@samsung.com>,
        =?UTF-8?B?QXJ0dXIgxZp3aWdvxYQ=?= <a.swigon@samsung.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-arm-msm@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230201101559.15529-1-johan+linaro@kernel.org>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20230201101559.15529-1-johan+linaro@kernel.org>
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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?

Best regards,
Krzysztof