On 7/27/21 11:50 PM, Viresh Kumar wrote:

On 27-07-21, 11:25, Thara Gopinath wrote:

quoted

+static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
+{

quoted

+	/* 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));
+}

quoted

+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)