From 7a215f89a0335582292ec6f3edaa3abd570da75a Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Fri, 30 Jan 2015 01:14:25 -0800 Subject: 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 Signed-off-by: Davidlohr Bueso Signed-off-by: Peter Zijlstra (Intel) Cc: Jason Low Cc: Linus Torvalds Cc: Michel Lespinasse Cc: Paul E. McKenney Cc: Tim Chen Link: http://lkml.kernel.org/r/1422609267-15102-4-git-send-email-dave@stgolabs.net Signed-off-by: Ingo Molnar --- kernel/locking/rwsem.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 kernel/locking/rwsem.h (limited to 'kernel/locking/rwsem.h') diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h new file mode 100644 index 000000000000..870ed9a5b426 --- /dev/null +++ b/kernel/locking/rwsem.h @@ -0,0 +1,20 @@ +#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 -- cgit v1.2.3