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

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Date:	Thu, 29 Jan 2009 21:35:17 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Cliff Wickman <cpw@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org, tj@...nel.org
Subject: Re: [PATCH] x86: UV cleanup


* 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?

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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