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Subject: Re: [PATCH, RFC] improved hacks to allow -rt to run kernbench on
	POWER
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: Peter Zijlstra <peterz@infradead.org>
Cc: paulmck@linux.vnet.ibm.com, Steven Rostedt <rostedt@goodmis.org>,
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       dino@in.ibm.com, tytso@us.ibm.com, dvhltc@us.ibm.com, niv@us.ibm.com,
       antonb@us.ibm.com, Ingo Molnar <mingo@elte.hu>
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Date: Tue, 13 Nov 2007 22:09:02 +1100
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On Tue, 2007-11-13 at 11:05 +0100, Peter Zijlstra wrote:
> Looking at the code:
> 
> /* radix tree not lockless safe ! we use a brlock-type mecanism
>  * for now, until we can use a lockless radix tree
>  */
> static void irq_radix_wrlock(unsigned long *flags)
> 
> The RCU radix tree stuffs have gone upstream long ago.
> 
> Anyway, it seems its the generic irq stuff that uses raw_spinlock_t
> and
> disables IRQs, so there isn't much we can do from the ARCH level I'm
> afraid :-(
> 
> Ingo, any sane ideas?

As discussed on IRC< there are a couple of other related issues, though
part of them go away if I can get rid of the brlock I have in there
thanks to the new RCU based radix tree.

I'll give that some thoughts and come back to you tomorrow or thursday
hopefully with a patch.

Cheers,
Ben.