linux-kernel - Re: [RFC PATCH v3 2/5] powerpc: Exception hooks for context tracking subsystem

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Message-ID: <1368438380.2618.52.camel@ThinkPad-T5421>
Date:	Mon, 13 May 2013 17:46:20 +0800
From:	Li Zhong <zhong@...ux.vnet.ibm.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	paulmck@...ux.vnet.ibm.com, fweisbec@...il.com, paulus@...ba.org,
	michael@...erman.id.au
Subject: Re: [RFC PATCH v3 2/5] powerpc: Exception hooks for context
 tracking subsystem

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.
> 
> 


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