lkml.org 
[lkml]   [2014]   [Aug]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] s390/locking: Reenable optimistic spinning
On Tue, Aug 05, 2014 at 09:57:51AM +0200, Christian Borntraeger wrote:
> 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

This can go in via the s390 tree. I applied your patch and changed
it a bit to keep Kconfig sorted.
Thanks!



\
 
 \ /
  Last update: 2014-08-06 10:41    [W:0.033 / U:25.684 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site