linux-kernel - [PATCH 1/2] locking/rwsem: Add CONFIG_RWSEM_SPIN_ON

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Date:	Fri,  6 Jun 2014 08:55:39 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	peterz@...radead.org, mingo@...nel.org
Cc:	mpatocka@...hat.com, torvalds@...ux-foundation.org,
	jason.low2@...com, waiman.long@...com, jejb@...isc-linux.org,
	paulmck@...ux.vnet.ibm.com, dave.anglin@...l.net, aswin@...com,
	davidlohr@...com, linux-kernel@...r.kernel.org,
	linux-parisc@...r.kernel.org
Subject: [PATCH 1/2] locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER

Just like with mutexes (CONFIG_MUTEX_SPIN_ON_OWNER),
encapsulate the dependencies for rwsem optimistic spinning.
No logical changes here as it continues to depend on both
SMP and the XADD algorithm variant.

Signed-off-by: Davidlohr Bueso <davidlohr@...com>
---
 include/linux/rwsem.h  | 4 ++--
 kernel/Kconfig.locks   | 4 ++++
 kernel/locking/rwsem.c | 2 +-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8d79708..accdef7 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -27,7 +27,7 @@ struct rw_semaphore {
 	long count;
 	raw_spinlock_t wait_lock;
 	struct list_head wait_list;
-#ifdef CONFIG_SMP
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 	/*
 	 * Write owner. Used as a speculative check to see
 	 * if the owner is running on the cpu.
@@ -64,7 +64,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 # define __RWSEM_DEP_MAP_INIT(lockname)
 #endif
 
-#if defined(CONFIG_SMP) && !defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 #define __RWSEM_INITIALIZER(name)			\
 	{ RWSEM_UNLOCKED_VALUE,				\
 	  __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 35536d9..e4c3162 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -224,6 +224,10 @@ config MUTEX_SPIN_ON_OWNER
 	def_bool y
 	depends on SMP && !DEBUG_MUTEXES
 
+config RWSEM_SPIN_ON_OWNER
+       def_bool y
+       depends on SMP && RWSEM_XCHGADD_ALGORITHM
+
 config ARCH_USE_QUEUE_RWLOCK
 	bool
 
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 42f806d..e2d3bc7 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -12,7 +12,7 @@
 
 #include <linux/atomic.h>
 
-#if defined(CONFIG_SMP) && defined(CONFIG_RWSEM_XCHGADD_ALGORITHM)
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 static inline void rwsem_set_owner(struct rw_semaphore *sem)
 {
 	sem->owner = current;
-- 
1.8.1.4

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