linux-kernel - Re: [patch 5/6] sparc: Use preempt_schedule

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Message-ID: <alpine.DEB.2.02.1309180120570.4089@ionos.tec.linutronix.de>
Date:	Wed, 18 Sep 2013 01:23:58 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Miller <davem@...emloft.net>
cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	linux-arch@...r.kernel.org, torvalds@...ux-foundation.org,
	ak@...ux.intel.com, hpa@...or.com, bitbucket@...ine.de,
	arjan@...ux.intel.com, fweisbec@...il.com
Subject: Re: [patch 5/6] sparc: Use preempt_schedule_irq

On Tue, 17 Sep 2013, David Miller wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> Date: Tue, 17 Sep 2013 18:53:08 -0000
> 
> >  		bne,pn			%xcc, kern_fpucheck
> > -		 sethi			%hi(PREEMPT_ACTIVE), %l6
> > -		stw			%l6, [%g6 + TI_PRE_COUNT]
> > -		call			schedule
> > +		call			preempt_schedule_irq
> >  		 nop
> 
> You've put the function call into the delay slot of the branch,
> which you don't want to do.
> 
> That's, btw, why we indent instructions with an extra space like
> that, to emphasize that it's a delay slot of the preceeding
> branch.

I knew that I'd get it wrong :) So is adding another nop the right
thing to do ?

 		bne,pn			%xcc, kern_fpucheck
-		 sethi			%hi(PREEMPT_ACTIVE), %l6
-		stw			%l6, [%g6 + TI_PRE_COUNT]
-		call			schedule
+  		 nop
+		call			preempt_schedule_irq
  		 nop
 
Thanks,

	tglx
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