lkml.org 
[lkml]   [2014]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] s390/locking: Reenable optimistic spinning
Date
commit 4badad352a6bb202ec68afa7a574c0bb961e5ebc (locking/mutex: Disable
optimistic spinning on some architectures) fenced spinning for
architectures without proper cmpxchg.
There is no need to disable mutex spinning on s390, though:
The instructions CS,CSG and friends provide the proper guarantees.
(We dont implement cmpxchg with locks).

Please note: This is a quick fix for s390, suitable for stable
as 3.16 unintenionally disabled optimistic spinning.

The proper fix is probably to use ARCH_HAVE_NMI_SAFE_CMPXCHG
instead of introducing ARCH_SUPPORTS_ATOMIC_RMW.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: stable@vger.kernel.org
---
arch/s390/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9a0ea87..eab3c32 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -63,6 +63,7 @@ config S390
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
select ARCH_HAVE_NMI_SAFE_CMPXCHG
+ select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_INLINE_READ_LOCK
select ARCH_INLINE_READ_LOCK_BH
select ARCH_INLINE_READ_LOCK_IRQ
--
1.8.4.2


\
 
 \ /
  Last update: 2014-08-05 10:41    [W:0.033 / U:1.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site