linux-kernel - Re: [tip:locking/urgent] locking/mutex: Disable optimistic spinning on some architectures

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Message-ID: <53C7B8AC.2040305@de.ibm.com>
Date:	Thu, 17 Jul 2014 13:51:08 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	mingo@...nel.org, dave.anglin@...l.net,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
CC:	torvalds@...ux-foundation.org, catalin.marinas@....com,
	peterz@...radead.org, cmetcalf@...era.com, jason.low2@...com,
	linux@....linux.org.uk, tglx@...utronix.de, davidlohr@...com,
	linux-kernel@...r.kernel.org, hpa@...or.com,
	James.Bottomley@...senpartnership.com, will.deacon@....com,
	waiman.long@...com, james.hogan@...tec.com, mpatocka@...hat.com,
	davem@...emloft.net, paulmck@...ux.vnet.ibm.com,
	vgupta@...opsys.com, benh@...nel.crashing.org,
	jejb@...isc-linux.org
Subject: Re: [tip:locking/urgent] locking/mutex:  Disable optimistic spinning
 on some architectures

s390: s390 also supports proper atomic read modify write,

There is no need to disable mutex spinning. The instructions 
CS,CSG and friends provide the proper guarantees. (We dont 
implement cmpxchg with locks).

Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
---
 arch/s390/Kconfig |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index bb63499..8c5df31 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
-- 
1.7.9.5

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