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[PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync

Started byDavidlohr Bueso <dave@stgolabs.net>
First post2016-03-22 00:30 +0100
Last post2016-03-23 09:40 +0100
Articles 2 — 2 participants

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  [PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync Davidlohr Bueso <dave@stgolabs.net> - 2016-03-22 00:30 +0100
    Re: [PATCH -tip] x86/mce: Use atomic_inc_return barrier when  starting monad sync Borislav Petkov <bp@alien8.de> - 2016-03-23 09:40 +0100

#1362210 — [PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync

FromDavidlohr Bueso <dave@stgolabs.net>
Date2016-03-22 00:30 +0100
Subject[PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync
Message-ID<rfhqO-4cX-5@gated-at.bofh.it>
mce_start() has an explicit smp_wmb to serialize writes to
global_nwo and mce_callin. However, atomic_inc_return() implies
barriers on both sides of the call, as such simply rely on this
full smp barrier.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index f0c921b03e42..6b7039c166b8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -830,9 +830,9 @@ static int mce_start(int *no_way_out)
 
 	atomic_add(*no_way_out, &global_nwo);
 	/*
-	 * global_nwo should be updated before mce_callin
+	 * Rely on the implied barrier below, such that global_nwo
+	 * is updated before mce_callin.
 	 */
-	smp_wmb();
 	order = atomic_inc_return(&mce_callin);
 
 	/*
-- 
2.1.4

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#1363242 — Re: [PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync

FromBorislav Petkov <bp@alien8.de>
Date2016-03-23 09:40 +0100
SubjectRe: [PATCH -tip] x86/mce: Use atomic_inc_return barrier when starting monad sync
Message-ID<rfMuD-KQ-7@gated-at.bofh.it>
In reply to#1362210
On Mon, Mar 21, 2016 at 04:19:56PM -0700, Davidlohr Bueso wrote:
> mce_start() has an explicit smp_wmb to serialize writes to
> global_nwo and mce_callin. However, atomic_inc_return() implies
> barriers on both sides of the call, as such simply rely on this
> full smp barrier.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied, thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

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