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From: Steven Noonan <steven@uplinklabs.net>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: Steven Noonan <steven@uplinklabs.net>,
	Ingo Molnar <mingo@elte.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	stable@vger.kernel.org
Subject: [PATCH v2] compiler/gcc4: make quirk for asm_volatile_goto unconditional
Date: Wed, 12 Feb 2014 23:01:07 -0800	[thread overview]
Message-ID: <1392274867-15236-1-git-send-email-steven@uplinklabs.net> (raw)
In-Reply-To: <1392274106.28471.2.camel@marge.simpson.net>

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.

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
---

v2: Adding stable@vger.kernel.org to Cc.

 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
-- 
1.8.5.4


  reply	other threads:[~2014-02-13  7:01 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-12 17:10 [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Ingo Molnar
2014-02-13  3:09 ` Steven Noonan
2014-02-13  4:11   ` Linus Torvalds
2014-02-13  4:53     ` [PATCH] compiler/gcc4: make quirk for asm_volatile_goto unconditional Steven Noonan
2014-02-13  6:48       ` Mike Galbraith
2014-02-13  7:01         ` Steven Noonan [this message]
2014-02-13 11:37           ` [tip:x86/urgent] compiler/gcc4: Make quirk for asm_volatile_goto( ) unconditional tip-bot for Steven Noonan
2014-02-13 11:55             ` Jakub Jelinek
2014-02-13 13:44               ` Steven Noonan
2014-07-10 15:00               ` Vlastimil Babka
2014-02-13  7:48     ` [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Jakub Jelinek
2014-02-13  9:43     ` Ingo Molnar

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