linux-kernel - [PATCH v2 2/3] x86: drop a comment left over from X86

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Date:	Wed, 13 Jan 2016 00:10:19 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Davidlohr Bueso <dave@...olabs.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Davidlohr Bueso <dbueso@...e.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	virtualization <virtualization@...ts.linux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Borislav Petkov <bp@...e.de>
Subject: [PATCH v2 2/3] x86: drop a comment left over from X86_OOSTORE

The comment about wmb being non-nop is a left over from before commit
09df7c4c8097 ("x86: Remove CONFIG_X86_OOSTORE").

It makes no sense now: if you have an SMP system with out of order
stores, making wmb not a nop will not help.

Additionally, wmb is not a nop even for regular intel CPUs because of
weird use-cases e.g. dealing with WC memory.

Drop this comment.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 arch/x86/include/asm/barrier.h | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index 7f99726..eb220b8 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -11,11 +11,6 @@
  */
 
 #ifdef CONFIG_X86_32
-/*
- * Some non-Intel clones support out of order store. wmb() ceases to be a
- * nop for these.
- */
-
 #define mb() asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
 #define rmb() alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
 #define wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
-- 
MST