linux-kernel - [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile

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Date:	Thu, 13 Feb 2014 03:37:08 -0800
From:	tip-bot for Steven Noonan <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	stable@...r.kernel.org, steven@...inklabs.net,
	akpm@...ux-foundation.org, rostedt@...dmis.org, jakub@...hat.com,
	oleg@...hat.com, tglx@...utronix.de, rth@...ddle.net
Subject: [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile_goto(
 ) unconditional

Commit-ID:  a9f180345f5378ac87d80ed0bea55ba421d83859
Gitweb:     http://git.kernel.org/tip/a9f180345f5378ac87d80ed0bea55ba421d83859
Author:     Steven Noonan <steven@...inklabs.net>
AuthorDate: Wed, 12 Feb 2014 23:01:07 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 13 Feb 2014 12:34:05 +0100

compiler/gcc4: Make quirk for asm_volatile_goto() unconditional

I started noticing problems with KVM guest destruction on Linux
3.12+, where guest memory wasn't being cleaned up. I bisected it
down to the commit introducing the new 'asm goto'-based atomics,
and found this quirk was later applied to those.

Unfortunately, even with GCC 4.8.2 (which ostensibly fixed the
known 'asm goto' bug) I am still getting some kind of
miscompilation. If I enable the asm_volatile_goto quirk for my
compiler, KVM guests are destroyed correctly and the memory is
cleaned up.

So make the quirk unconditional for now, until bug is found
and fixed.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Steven Noonan <steven@...inklabs.net>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Jakub Jelinek <jakub@...hat.com>
Cc: Richard Henderson <rth@...ddle.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: <stable@...r.kernel.org>
Link: http://lkml.kernel.org/r/1392274867-15236-1-git-send-email-steven@uplinklabs.net
Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 include/linux/compiler-gcc4.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index ded4299..2507fd2 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -75,11 +75,7 @@
  *
  * (asm goto is automatically volatile - the naming reflects this.)
  */
-#if GCC_VERSION <= 40801
-# define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
-#else
-# define asm_volatile_goto(x...)	do { asm goto(x); } while (0)
-#endif
+#define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
 
 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
 #if GCC_VERSION >= 40400
--
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