linux-kernel - Re: [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with irqs disabled

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Date:	Sun, 24 Jul 2011 11:00:41 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, laijs@...fujitsu.com,
	darren@...art.com, rostedt@...dmis.org, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with
 irqs disabled

On Sat, 23 Jul 2011, Paul E. McKenney wrote:
> On Sun, Jul 24, 2011 at 02:05:13AM +0200, Thomas Gleixner wrote:
> > On Sun, 24 Jul 2011, Thomas Gleixner wrote:
> > > > > Thomas, I'm inclined to merge this, any objections?
> > > > 
> > > > FWIW, it has been passing tests here.
> > > 
> > > If it's only the unlock path, I'm fine with that change.
> > > 
> > > Acked-by-me
> > 
> > Hrmpft. That's requiring all places to take the lock irq safe. Not
> > really amused. For -RT that's a hotpath and we can really do without
> > the irq fiddling there. That needs a bit more thought.
> 
> Indeed...  If I make only some of the lock acquisitions irq safe, lockdep
> will yell at me.  And rightfully so, as that could result in deadlock.
> 
> So, what did you have in mind?

Have no real good idea yet for this. Could you grab rt and check
whether you can observe any impact when the patch is applied?

Thanks,

	tglx
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