On Mon, Nov 15, 2021 at 10:35:23PM +0000, Winiarska, Iwona wrote:

On Mon, 2021-11-15 at 19:49 +0100, Greg Kroah-Hartman wrote:

quoted

On Mon, Nov 15, 2021 at 07:25:45PM +0100, Iwona Winiarska wrote:

quoted

+void peci_device_destroy(struct peci_device *device)
+{
+       bool killed;
+
+       device_lock(&device->dev);
+       killed = kill_device(&device->dev);

Eeek, why call this?

quoted

+       device_unlock(&device->dev);
+
+       if (!killed)
+               return;

What happened if something changed after you unlocked it?

We either killed it, or the other caller killed it.

quoted

Why is kill_device() required at all?  That's a very rare function to
call, and one that only one "bus" calls today because it is very
special (i.e. crazy and broken...)

It's used to avoid double-delete in case of races between peci_controller
unregister and "manually" removing the device using sysfs (pointed out by Dan in
v2). We're calling peci_device_destroy() in both callsites.
Other way to solve it would be to just have a peci-specific lock, but
kill_device seemed to be well suited for the problem at hand.
Do you suggest to remove it and just go with the lock?

Yes please, remove it and use the lock.

Also, why are you required to have a sysfs file that can remove the
device?  Who wants that?

thanks,

greg k-h