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Subject: Re: [RFC PATCH v3 2/5] powerpc: Exception hooks for context
 tracking subsystem
From: Li Zhong <zhong@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Mon, 13 May 2013 17:46:20 +0800
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On Mon, 2013-05-13 at 19:06 +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2013-05-13 at 16:44 +0800, Li Zhong wrote:
> > Yes, the above and hash_page() are two C functions for a same exception.
> > And the exception hooks enable RCU usage in those C codes. But for asm
> > codes, I think we could assume that there would be no RCU usage there,
> > so we don't need wrap them in the hooks.
> 
> hash_page() won't start a new RCU, at least not in its current incarnation,
> the only thing I can see it ever doing would be to take some RCU read locks one
> day (it doesn't today).

Seems I added the hooks because of the trace point of hcall
entry/exit ...

Thanks, Zhong

> 
> low_hash_fault() is a different beast. It will typically kill things, thus
> involving sending signals etc... RCU might well be involved.
> 
> Cheers,
> Ben.
> 
>