linux-kernel - [PATCH] s390/locking: Reenable optimistic spinning

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1407225471-14875-1-git-send-email-borntraeger@de.ibm.com>
Date:	Tue,  5 Aug 2014 09:57:51 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-s390@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	heiko.carstens@...ibm.com,
	Christian Borntraeger <borntraeger@...ibm.com>,
	<mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	stable@...r.kernel.org
Subject: [PATCH] s390/locking: Reenable optimistic spinning

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@...ibm.com>
CC: <mingo@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: stable@...r.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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/