linux/kernel/locking/rwsem.h

#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
static inline void rwsem_set_owner(struct rw_semaphore *sem)
{
	sem->owner = current;
}

static inline void rwsem_clear_owner(struct rw_semaphore *sem)
{
	sem->owner = NULL;
}

#else
static inline void rwsem_set_owner(struct rw_semaphore *sem)
{
}

static inline void rwsem_clear_owner(struct rw_semaphore *sem)
{
}
#endif
locking/rwsem: Set lock ownership ASAP In order to optimize the spinning step, we need to set the lock owner as soon as the lock is acquired; after a successful counter cmpxchg operation, that is. This is particularly useful as rwsems need to set the owner to nil for readers, so there is a greater chance of falling out of the spinning. Currently we only set the owner much later in the game, in the more generic level -- latency can be specially bad when waiting for a node->next pointer when releasing the osq in up_write calls. As such, update the owner inside rwsem_try_write_lock (when the lock is obtained after blocking) and rwsem_try_write_lock_unqueued (when the lock is obtained while spinning). This requires creating a new internal rwsem.h header to share the owner related calls. Also cleanup some headers for mutex and rwsem. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Jason Low <jason.low2@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michel Lespinasse <walken@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Link: http://lkml.kernel.org/r/1422609267-15102-4-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar <mingo@kernel.org> 2015-01-30 01:14:25 -08:00			`#ifdef CONFIG_RWSEM_SPIN_ON_OWNER`
			`static inline void rwsem_set_owner(struct rw_semaphore *sem)`
			`{`
			`sem->owner = current;`
			`}`

			`static inline void rwsem_clear_owner(struct rw_semaphore *sem)`
			`{`
			`sem->owner = NULL;`
			`}`

			`#else`
			`static inline void rwsem_set_owner(struct rw_semaphore *sem)`
			`{`
			`}`

			`static inline void rwsem_clear_owner(struct rw_semaphore *sem)`
			`{`
			`}`
			`#endif`