linux-kernel - Re: [RFC PATCH v2 2/6] powerpc: Exception hooks for context tracking subsystem

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Date:	Fri, 5 Apr 2013 13:50:25 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	paulmck@...ux.vnet.ibm.com, fweisbec@...il.com,
	benh@...nel.crashing.org
Subject: Re: [RFC PATCH v2 2/6] powerpc: Exception hooks for context tracking
 subsystem

On Fri, Mar 29, 2013 at 06:00:17PM +0800, Li Zhong wrote:
> This is the exception hooks for context tracking subsystem, including
> data access, program check, single step, instruction breakpoint, machine check,
> alignment, fp unavailable, altivec assist, unknown exception, whose handlers
> might use RCU.
> 
> This patch corresponds to
> [PATCH] x86: Exception hooks for userspace RCU extended QS
>   commit 6ba3c97a38803883c2eee489505796cb0a727122
> 
> Signed-off-by: Li Zhong <zhong@...ux.vnet.ibm.com>

Is there a reason why you didn't put the exception_exit() call in
ret_from_except_lite in entry_64.S, and the exception_entry() call in
EXCEPTION_PROLOG_COMMON?  That would seem to catch all these cases in
a more centralized place.

Also, I notice that with the exception_exit calls where they are, we
can still deliver signals (thus possibly taking a page fault) or call
schedule() for preemption after the exception_exit() call.  Is that
OK, or is it a potential problem?

Paul.
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