linux-kernel - Re: [PATCH] sched: Support current clocksource handling in fallback sched

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Message-ID: <alpine.LFD.2.00.0905281450480.3397@localhost.localdomain>
Date:	Thu, 28 May 2009 14:53:11 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Paul Mundt <lethal@...ux-sh.org>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Daniel Walker <dwalker@...o99.com>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Victor <linux@...im.org.za>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	John Stultz <johnstul@...ux.vnet.ibm.com>
Subject: Re: [PATCH] sched: Support current clocksource handling in fallback
 sched_clock().

On Thu, 28 May 2009, Paul Mundt wrote:

> On Thu, May 28, 2009 at 02:22:17PM +0200, Thomas Gleixner wrote:
> > On Thu, 28 May 2009, Paul Mundt wrote:
> > > @@ -437,10 +441,19 @@ void clocksource_unregister(struct clocksource *cs)
> > >  	unsigned long flags;
> > >  
> > >  	spin_lock_irqsave(&clocksource_lock, flags);
> > > +
> > > +	if (sched_clocksource == cs) {
> > > +		printk(KERN_WARNING "Refusing to unregister "
> > > +		       "scheduler clocksource %s", cs->name);
> > 
> >   Hmm, isn't that dangerous ? The clocksource might be in a module or
> >   in kmalloced memory which is going to be freed.
> > 
> Perhaps the saner thing to do is see if select_clocksource() manages to
> find something suitable, otherwise switch back to jiffies..

That makes sense. The scheduler should be able handle that, if not ... :)
 
Thanks,

	tglx
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