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From: Thara Gopinath <thara.gopinath@linaro.org>
To: Viresh Kumar <viresh.kumar@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, steev@kali.org,
	linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [Patch v4 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt support
Date: Wed, 28 Jul 2021 18:19:05 -0400	[thread overview]
Message-ID: <9a257605-d282-cd06-cc44-5ad5a5f8484d@linaro.org> (raw)
In-Reply-To: <20210728035014.25mgvrpnraxfslq7@vireshk-i7>



On 7/27/21 11:50 PM, Viresh Kumar wrote:
> On 27-07-21, 11:25, Thara Gopinath wrote:
>> +static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
>> +{
> 
>> +	/* In the unlikely case cpufreq is de-registered do not enable polling or h/w interrupt */
>> +
>> +	spin_lock(&data->throttle_lock);
>> +	if (data->cancel_throttle) {
>> +		spin_unlock(&data->throttle_lock);
>> +		return;
>> +	}
>> +	spin_unlock(&data->throttle_lock);
>> +
>> +	/*
>> +	 * If h/w throttled frequency is higher than what cpufreq has requested for, stop
>> +	 * polling and switch back to interrupt mechanism
>> +	 */
>> +
>> +	if (throttled_freq >= qcom_cpufreq_hw_get(cpumask_first(policy->cpus)))
>> +		/* Clear the existing interrupts and enable it back */
>> +		enable_irq(data->throttle_irq);
>> +	else
>> +		mod_delayed_work(system_highpri_wq, &data->throttle_work,
>> +				 msecs_to_jiffies(10));
>> +}
> 
>> +static void qcom_cpufreq_hw_lmh_exit(struct qcom_cpufreq_data *data)
>> +{
>> +	if (data->throttle_irq <= 0)
>> +		return;
>> +
>> +	spin_lock(&data->throttle_lock);
>> +	data->cancel_throttle = true;
>> +	spin_unlock(&data->throttle_lock);
>> +	cancel_delayed_work_sync(&data->throttle_work);
>> +	free_irq(data->throttle_irq, data);
>> +}
> 
> Lets see if we can still make it break :)
> 
> CPU0                                            CPU1
> 
> qcom_lmh_dcvs_notify()                          qcom_cpufreq_hw_lmh_exit()
> 
> spin_unlock()
>                                                  spin_lock(),
>                                                  cancel_throttle = true
>                                                  spin_unlock()
> 
>                                                  cancel_delayed_work_sync()
> mod_delayed_work()
>                                                  free_irq()
>                                                  kfree(data)
> qcom_lmh_dcvs_poll()
> Uses data.
> 
> 
> Sorry, locking is fun :)

Ha! I was too lazy to write this down! So how about I make this a mutex 
and put mod_delayed_work() inside the lock. So it will be something like 
below

qcom_lmh_dcvs_notify()			qcom_cpufreq_hw_lmh_exit()

mutex_lock()				mutex_lock()
   if (data->cancel_throttle) {		cancel_throttle = true
	mutex_unlock()			mutex_unlock()
	return				cancel_delayed_work_sync()
   }					free_irq()
   enable_irq() / mod_delayed_work()
mutex_unlock()

I will let you break it!

> 

-- 
Warm Regards
Thara (She/Her/Hers)

  reply	other threads:[~2021-07-28 22:19 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 15:25 [Patch v4 0/6] Introduce LMh driver for Qualcomm SoCs Thara Gopinath
2021-07-27 15:25 ` [Patch v4 1/6] firmware: qcom_scm: Introduce SCM calls to access LMh Thara Gopinath
2021-07-27 15:25 ` [Patch v4 2/6] thermal: qcom: Add support for LMh driver Thara Gopinath
2021-07-27 15:25 ` [Patch v4 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt support Thara Gopinath
2021-07-28  3:50   ` Viresh Kumar
2021-07-28 22:19     ` Thara Gopinath [this message]
2021-07-29  6:17       ` Viresh Kumar
2021-07-29 11:13         ` Thara Gopinath
2021-07-29 11:15           ` Viresh Kumar
2021-07-27 15:25 ` [Patch v4 4/6] arm64: dts: qcom: sdm45: Add support for LMh node Thara Gopinath
2021-07-27 15:25 ` [Patch v4 5/6] arm64: dts: qcom: sdm845: Remove cpufreq cooling devices for CPU thermal zones Thara Gopinath
2021-07-27 15:25 ` [Patch v4 6/6] dt-bindings: thermal: Add dt binding for QCOM LMh Thara Gopinath
2021-07-27 18:26   ` Rob Herring
2021-07-28 16:10   ` Rob Herring
2021-08-02 21:29     ` Thara Gopinath
2021-07-27 17:44 ` [Patch v4 0/6] Introduce LMh driver for Qualcomm SoCs Steev Klimaszewski

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