Both waiter_spinning and yield_to_waiter are used for somewhat similar purpose. The waiter_spinning flag is used in CONFIG_MUTEX_SPIN_ON_OWNER to make optimistic spinner yield to spinning waiter; whereas the yield_to_waiter is used in !CONFIG_MUTEX_SPIN_ON_OWNER to make new incoming mutex locker to yield to the sleeping waiter.
This patch unifies these 2 flags into a single yield_to_waiter flag that is used in both CONFIG_MUTEX_SPIN_ON_OWNER and !CONFIG_MUTEX_SPIN_ON_OWNER codes. Signed-off-by: Waiman Long <[email protected]> --- include/linux/mutex.h | 8 ++++++-- kernel/locking/mutex.c | 12 ++++++------ 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 988c020..2b3dcdb 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -57,8 +57,12 @@ struct mutex { #endif #ifdef CONFIG_MUTEX_SPIN_ON_OWNER struct optimistic_spin_queue osq; /* Spinner MCS lock */ - int waiter_spinning; -#elif defined(CONFIG_SMP) +#endif +#ifdef CONFIG_SMP + /* + * Used by both CONFIG_MUTEX_SPIN_ON_OWNER (depends on CONFIG_SMP) & + * !CONFIG_MUTEX_SPIN_ON_OWNER codes. + */ int yield_to_waiter; #endif #ifdef CONFIG_DEBUG_MUTEXES diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index c4261fa..7218835 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -55,8 +55,8 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) mutex_clear_owner(lock); #ifdef CONFIG_MUTEX_SPIN_ON_OWNER osq_lock_init(&lock->osq); - lock->waiter_spinning = false; -#elif defined(CONFIG_SMP) +#endif +#ifdef CONFIG_SMP lock->yield_to_waiter = false; #endif @@ -351,7 +351,7 @@ static bool mutex_optimistic_spin(struct mutex *lock, * Turn on the waiter spinning flag to discourage the spinner * from getting the lock. */ - lock->waiter_spinning = true; + lock->yield_to_waiter = true; } for (;;) { @@ -374,11 +374,11 @@ static bool mutex_optimistic_spin(struct mutex *lock, } /* - * For regular opt-spinner, it waits until the waiter_spinning + * For regular opt-spinner, it waits until the yield_to_waiter * flag isn't set. This will ensure forward progress for * the waiter spinner. */ - if (!waiter && READ_ONCE(lock->waiter_spinning)) { + if (!waiter && READ_ONCE(lock->yield_to_waiter)) { if (need_resched()) break; goto relax; @@ -430,7 +430,7 @@ relax: if (!waiter) osq_unlock(&lock->osq); else - lock->waiter_spinning = false; + lock->yield_to_waiter = false; done: /* * If we fell out of the spin path because of need_resched(), -- 1.7.1
