linux-kernel - [tip:locking/core] locking/x86: Tweak the comment about use of wmb() for IO

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Date:	Fri, 29 Jan 2016 03:32:52 -0800
From:	"tip-bot for Michael S. Tsirkin" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, dbueso@...e.de, tglx@...utronix.de,
	andreyknvl@...gle.com, hpa@...or.com, paulmck@...ux.vnet.ibm.com,
	peterz@...radead.org, dave@...olabs.net, brgerst@...il.com,
	bp@...en8.de, virtualization@...ts.linux-foundation.org,
	mingo@...nel.org, luto@...nel.org, torvalds@...ux-foundation.org,
	mst@...hat.com, akpm@...ux-foundation.org, luto@...capital.net,
	bp@...e.de, dvlasenk@...hat.com
Subject: [tip:locking/core] locking/x86:
  Tweak the comment about use of wmb() for IO

Commit-ID:  57d9b1b43433a6ba7267c80b87d8e8f6e86edceb
Gitweb:     http://git.kernel.org/tip/57d9b1b43433a6ba7267c80b87d8e8f6e86edceb
Author:     Michael S. Tsirkin <mst@...hat.com>
AuthorDate: Thu, 28 Jan 2016 19:02:44 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 29 Jan 2016 09:40:10 +0100

locking/x86: Tweak the comment about use of wmb() for IO

On x86, we *do* still use the non-NOP rmb()/wmb() for IO barriers,
but even that is generally questionable.

Leave them around as historial unless somebody can point to a
case where they care about the performance, but tweak the
comment so people don't think they are strictly required in all
cases.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Davidlohr Bueso <dbueso@...e.de>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: virtualization <virtualization@...ts.linux-foundation.org>
Link: http://lkml.kernel.org/r/1453921746-16178-4-git-send-email-mst@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/barrier.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index a291745..bfb28ca 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -6,7 +6,7 @@
 
 /*
  * Force strict CPU ordering.
- * And yes, this is required on UP too when we're talking
+ * And yes, this might be required on UP too when we're talking
  * to devices.
  */