Re: [PATCH v8 4/8] PM / EM: add support for other devices than CPUs in Energy Model

From: Lukasz Luba
Date: Tue Jun 02 2020 - 07:31:43 EST

Hi Daniel,

On 6/1/20 10:44 PM, Daniel Lezcano wrote:
On 27/05/2020 11:58, Lukasz Luba wrote:
Add support for other devices than CPUs. The registration function
does not require a valid cpumask pointer and is ready to handle new
devices. Some of the internal structures has been reorganized in order to
keep consistent view (like removing per_cpu pd pointers).

Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>

[ ... ]

+ * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
+ * @dev : Device for which the EM is registered
+ *
+ * Try to unregister the EM for the specified device (but not a CPU).
+ */
+void em_dev_unregister_perf_domain(struct device *dev)
+ if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
+ return;
+ if (_is_cpu_device(dev))
+ return;
+ mutex_lock(&em_pd_mutex);

Is the mutex really needed?

I just wanted to align this unregister code with register. Since there
is debugfs dir lookup and the device's EM existence checks I thought it
wouldn't harm just to lock for a while and make sure the registration
path is not used. These two paths shouldn't affect each other, but with
modules loading/unloading I wanted to play safe.
I can change it maybe to just dmb() and the end of the function if it's
a big performance problem in this unloading path. What do you think?

If this function is called that means there is no more user of the
em_pd, no?

True, that EM users should already be unregistered i.e. thermal cooling.

+ em_debug_remove_pd(dev);
+ kfree(dev->em_pd->table);
+ kfree(dev->em_pd);
+ dev->em_pd = NULL;
+ mutex_unlock(&em_pd_mutex);

Thank you for reviewing this.