linux-kernel - Re: [PATCH] [RFC] kernel/cpu: Use lockref for online CPU reference counting

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Message-ID: <20160217142005.GD6357@twins.programming.kicks-ass.net>
Date:	Wed, 17 Feb 2016 15:20:05 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Intel graphics driver community testing & development 
	<intel-gfx@...ts.freedesktop.org>,
	Linux kernel development <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] [RFC] kernel/cpu: Use lockref for online CPU reference
 counting

On Wed, Feb 17, 2016 at 02:47:31PM +0200, Joonas Lahtinen wrote:
> On ti, 2016-02-16 at 12:07 +0100, Peter Zijlstra wrote:
> > On Tue, Feb 16, 2016 at 12:51:03PM +0200, Joonas Lahtinen wrote:
> > > Quoting my original patch;
> > > 
> > > "See the Bugzilla link for more details.
> > 
> > If its not in the Changelog it doesn't exist. Patches should be self
> > contained and not refer to external sources for critical information.
> 
> The exact locking case in CPUfreq drivers causing a splat is described
> in the patch. Details were already included, that's why term "more
> details" was used.

Barely. What was not described was why you went to tinker with the
hotplug lock instead of sanitizing cpufreq. Nor why your chosen solution
is good.

> This is not exactly taking us closer to a fix, 

Why you think we can discuss fixes if you've not actually described your
problem is beyond me.