linux-kernel - [PATCH] x86, MCE, AMD: move invariant code out from loop body

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Message-ID: <1412263212.8085.6.camel@debian>
Date:	Thu, 02 Oct 2014 23:20:12 +0800
From:	Chen Yucong <slaoub@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Tony Luck <tony.luck@...il.com>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86, MCE, AMD: move invariant code out from loop body

On Thu, 2014-10-02 at 16:38 +0200, Borislav Petkov wrote:
> 
> On Mon, Sep 22, 2014 at 09:11:00PM +0200, Borislav Petkov wrote:
> > On Mon, Sep 22, 2014 at 05:23:32PM +0800, Chen Yucong wrote:
> > >  Hi Boris,
> > > 
> > > I have found the following code snippet in mce_amd.c. 
> > > 
> > > /* cpu init entry point, called from mce.c with preempt off */
> > > void mce_amd_feature_init(struct cpuinfo_x86 *c)
> > > {
> > >         ... ...
> > >         for (bank = 0; bank < mca_cfg.banks; ++bank) {
> > >                 for (block = 0; block < NR_BLOCKS; ++block) {
> > >                         ... ...
> > >                         mce_threshold_block_init(&b, offset);
> > >                         mce_threshold_vector = amd_threshold_interrupt;
> > >                 }
> > >         }
> > > }
> > > 
> > > Why should "mce_threshold_vector = amd_threshold_interrupt" be placed in
> > > the inner loop body?
> > 
> > Yeah, it was added sloppily with b276268631af3, I'm not surprised. Feel
> > free to send a fix.
> 
> do you still want to send a fix or should I fix it up quickly?
> 

From: Chen Yucong <slaoub@...il.com>
Subject: [PATCH] x86, MCE, AMD: move invariant code out from loop body

"mce_threshold_vector = amd_threshold_interrupt;" is loop invariant code
in mce_amd_feature_init(). So it should be moved out from loop body.

Signed-off-by: Chen Yucong <slaoub@...il.com>
---
 arch/x86/kernel/cpu/mcheck/mce_amd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index 5d4999f..f727701 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -253,9 +253,10 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c)
 			}
 
 			mce_threshold_block_init(&b, offset);
-			mce_threshold_vector = amd_threshold_interrupt;
 		}
 	}
+
+	mce_threshold_vector = amd_threshold_interrupt;
 }
 
 /*
-- 
1.7.10.4




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