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Date:   Tue, 13 Jul 2021 08:48:48 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Thara Gopinath <thara.gopinath@linaro.org>
Cc:     agross@kernel.org, bjorn.andersson@linaro.org, rui.zhang@intel.com,
        daniel.lezcano@linaro.org, rjw@rjwysocki.net, robh+dt@kernel.org,
        tdas@codeaurora.org, mka@chromium.org,
        linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [Patch v3 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt
 support
Message-ID: <20210713031848.sp5fpjg36uthnmuq@vireshk-i7>
References: <20210708120656.663851-1-thara.gopinath@linaro.org>
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On 12-07-21, 21:18, Thara Gopinath wrote:
> So I really need the interrupt to fire and then the timer to kick in and
> take up the monitoring. I can think of introducing a variable is_disabled
> which is updated and read under a spinlock. qcom_cpufreq_hw_cpu_exit can
> hold the spinlock and set is_disabled to true prior to cancelling the work
> queue or disabling the interrupt. Before re-enabling the interrupt or
> re-queuing the work in qcom_lmh_dcvs_notify, is_disabled can be read and
> checked.

Or you can make the lmh_dcvs_poll_work item a pointer and mark it NULL in exit,
with proper locking etc.

> But does this problem not exist in target_index , fast_switch etc also ? One
> cpu can be disabling and the other one can be updating the target right?

The race doesn't happen there as cpufreq_unregister_driver() takes care of
stopping everything before removing the policy. To be more precise, governor's
->stop() function is responsible for making sure that frequency won't be updated
any further.

-- 
viresh