linux-kernel - Re: [PATCH v2] cpufreq: Avoid attempts to create duplicate symbolic links

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Date:	Wed, 29 Jul 2015 03:38:03 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH v2] cpufreq: Avoid attempts to create duplicate symbolic links

On Monday, July 27, 2015 08:09:35 PM Viresh Kumar wrote:
> On 27-07-15, 15:45, Rafael J. Wysocki wrote:
> > Say the subsys add callback runs for a CPU and it doesn't have a policy.
> > If it is offline, we ignore it and the add callback won't be executed
> > for it again.
> > 
> > In turn, if it is online, we create a policy for it and we should (right
> > away) link the policy to all of the CPUs that were offline when the subsys add
> > callback was called for them.  That's what we do today.
> > 
> > Is there anything missing in that?
> 
> So the code is working properly after your patch, but I was talking
> on the lines of what Russell suggested.
> 
> We should play with the links only when we receive add-dev/remove-dev
> from subsys callbacks. The exception to that will be the offline CPUs
> for which add-dev is called before their policy existed.

The rule is supposed to be "all of the present CPUs which do not own
a policy should point to one, unless it doesn't exist".  The right
approach is then to create links from them to a policy object as soon
as we create one for them.  Waiting for something else to happen is just
pointless and this approach covers both the offline and online CPUs, so
I don't think that changing it would improve things really.

Thanks,
Rafael

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