[PATCH] x86: UV cleanup

[PATCH] x86: UV cleanup

[Cliff Wickman]

From: Cliff Wickman <cpw@sgi.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.

Diffed against 2.6.29-rc2
  (Ingo's tree)

Signed-off-by: Cliff Wickman <cpw@sgi.com>
---
 arch/x86/kernel/tlb_uv.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux/arch/x86/kernel/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/kernel/tlb_uv.c
+++ linux/arch/x86/kernel/tlb_uv.c
@@ -259,7 +259,7 @@ const struct cpumask *uv_flush_send_and_
 		 * the cpu's, all of which are still in the mask.
 		 */
 		__get_cpu_var(ptcstats).ptc_i++;
-		return 0;
+		return flush_mask;
 	}
 
 	/*
@@ -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
 
 	cpumask_andnot(flush_mask, cpumask, cpumask_of(cpu));
 

Re: [PATCH] x86: UV cleanup

[Ingo Molnar]

* Cliff Wickman <cpw@sgi.com> wrote:

> From: Cliff Wickman <cpw@sgi.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

Re: [PATCH] x86: UV cleanup

[Cliff Wickman]

On Thu, Jan 29, 2009 at 09:35:17PM +0100, Ingo Molnar wrote:
> 
> * Cliff Wickman <cpw@sgi.com> wrote:
> 
> > From: Cliff Wickman <cpw@sgi.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
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

-- 
Cliff Wickman
Silicon Graphics, Inc.
cpw@sgi.com
(651) 683-3824