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Commit 5db6c6fe authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Ingo Molnar
Browse files

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: default avatarDavidlohr Bueso <davidlohr@hp.com>
Acked-by: default avatarJason Low <jason.low2@hp.com>
[ Also make it depend on ARCH_SUPPORTS_ATOMIC_RMW. ]
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1405112406-13052-2-git-send-email-davidlohr@hp.com


Cc: aswin@hp.com
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>

Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4badad35

include/linux/rwsem.h

+4 −2
Original line number Diff line number Diff line
@@ -14,7 +14,9 @@ 
#include <linux/list.h>

#include <linux/spinlock.h>

#include <linux/atomic.h>

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER

#include <linux/osq_lock.h>

#endif



struct rw_semaphore;
@@ -26,7 +28,7 @@ struct rw_semaphore { 
	long count;

	struct list_head wait_list;

	raw_spinlock_t wait_lock;

#ifdef CONFIG_SMP

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER

	struct optimistic_spin_queue osq; /* spinner MCS lock */

	/*

	 * Write owner. Used as a speculative check to see
@@ -63,7 +65,7 @@ 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_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL

#else

#define __RWSEM_OPT_INIT(lockname)

kernel/Kconfig.locks

+4 −0
Original line number Diff line number Diff line
@@ -227,6 +227,10 @@ config MUTEX_SPIN_ON_OWNER 
	def_bool y

	depends on SMP && !DEBUG_MUTEXES && ARCH_SUPPORTS_ATOMIC_RMW



config RWSEM_SPIN_ON_OWNER

       def_bool y

       depends on SMP && RWSEM_XCHGADD_ALGORITHM && ARCH_SUPPORTS_ATOMIC_RMW



config ARCH_USE_QUEUE_RWLOCK

	bool

kernel/locking/rwsem-xadd.c

+2 −2
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name, 
	sem->count = RWSEM_UNLOCKED_VALUE;

	raw_spin_lock_init(&sem->wait_lock);

	INIT_LIST_HEAD(&sem->wait_list);

#ifdef CONFIG_SMP

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER

	sem->owner = NULL;

	osq_lock_init(&sem->osq);

#endif
@@ -262,7 +262,7 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem) 
	return false;

}



#ifdef CONFIG_SMP

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER

/*

 * Try to acquire write lock before the writer has been put on wait queue.

 */

kernel/locking/rwsem.c

+1 −1
Original line number Diff line number Diff line
@@ -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;