From mboxrd@z Thu Jan  1 00:00:00 1970
From: Winiarska, Iwona <iwona.winiarska@intel.com>
Date: Mon, 15 Nov 2021 22:35:23 +0000
Subject: [PATCH v3 06/13] peci: Add device detection
In-Reply-To: <YZKr1Rqfx6Cmw+Ok@kroah.com>
References: <20211115182552.3830849-1-iwona.winiarska@intel.com>
 <20211115182552.3830849-7-iwona.winiarska@intel.com>
 <YZKr1Rqfx6Cmw+Ok@kroah.com>
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On Mon, 2021-11-15 at 19:49 +0100, Greg Kroah-Hartman wrote:
> On Mon, Nov 15, 2021 at 07:25:45PM +0100, Iwona Winiarska wrote:
> > +void peci_device_destroy(struct peci_device *device)
> > +{
> > +???????bool killed;
> > +
> > +???????device_lock(&device->dev);
> > +???????killed = kill_device(&device->dev);
> 
> Eeek, why call this?
> 
> > +???????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.

> 
> 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?

Thanks
-Iwona

> 
> thanks,
> 
> greg k-h