linux-kernel - [PATCH 3/3] s390: enable ARCH_USE_CMPXCHG

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Message-Id: <1380269034-38521-4-git-send-email-heiko.carstens@de.ibm.com>
Date:	Fri, 27 Sep 2013 10:03:54 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Tony Luck <tony.luck@...el.com>, Waiman Long <waiman.long@...com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: [PATCH 3/3] s390: enable ARCH_USE_CMPXCHG_LOCKREF

Enable ARCH_USE_CMPXCHG_LOCKREF for 64 bit since it shows performance
improvements with Linus' simple stat() test case of up to 50% on a
30 cpu system.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
 arch/s390/Kconfig                | 1 +
 arch/s390/include/asm/spinlock.h | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9789282..6651695 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -93,6 +93,7 @@ config S390
 	select ARCH_INLINE_WRITE_UNLOCK_IRQ
 	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 	select ARCH_SAVE_PAGE_KEYS if HIBERNATION
+	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
 	select CLONE_BACKWARDS2
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 701fe8c..83e5d216 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -44,6 +44,11 @@ extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
 extern int arch_spin_trylock_retry(arch_spinlock_t *);
 extern void arch_spin_relax(arch_spinlock_t *lock);
 
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+	return lock.owner_cpu == 0;
+}
+
 static inline void arch_spin_lock(arch_spinlock_t *lp)
 {
 	int old;
-- 
1.8.3.4

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