linux-kernel - Re: [PATCH] x86: UV cleanup

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Message-ID: <20090129213029.GA29154@sgi.com>
Date:	Thu, 29 Jan 2009 15:30:29 -0600
From:	Cliff Wickman <cpw@....com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, tj@...nel.org
Subject: Re: [PATCH] x86: UV cleanup


On Thu, Jan 29, 2009 at 09:35:17PM +0100, Ingo Molnar wrote:
> 
> * Cliff Wickman <cpw@....com> wrote:
> 
> > From: Cliff Wickman <cpw@....com>
> > 
> > This patch tweaks a couple things:
> > 
> > - uv_flush_tlb_others()
> >   the WARN_ON(!in_atomic()); fails if CONFIG_PREEMPT is not enabled
> > 
> >   The #ifdef may not be the right fix. The fix is probably in the
> >   in_atomic macro, but I'm not sure what in_atomic() should return
> >   if CONFIG_PREEMPT is turned off.  I tested making it return 1 in that
> >   case, but that yielded tons of warnings.
> > 
> >   The simpler fix for tlb_uv.c would be to just drop the WARN_ON.
> > 
> > - uv_flush_send_and_wait() should return a pointer if the broadcast
> >   remote tlb shootdown requests fail. That causes the conventional IPI
> >   method of shootdown to be used.
> 
> hm, this isnt a cleanup but a fix - i.e. needs to go into x86/urgent as a 
> separate patch, right?

Yes, it is a fix.  I'll re-post, and send the WARN_ON issue as a
separate patch.

 
> and this:
> 
> > @@ -316,7 +316,9 @@ const struct cpumask *uv_flush_tlb_other
> >  	int locals = 0;
> >  	struct bau_desc *bau_desc;
> >  
> > +#ifdef CONFIG_PREEMPT
> >  	WARN_ON(!in_atomic());
> > +#endif
> 
> is indeed somewhat ugly - and we have no proper primitive to test for 
> atomicity. (mainly because we dont know about atomicity on a non-preempt 
> kernel)
> 
> 	Ingo
> --
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-- 
Cliff Wickman
Silicon Graphics, Inc.
cpw@....com
(651) 683-3824
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