From 95c354fe9f7d6decc08a92aa26eb233ecc2155bf Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 30 Jan 2008 13:31:20 +0100 Subject: spinlock: lockbreak cleanup The break_lock data structure and code for spinlocks is quite nasty. Not only does it double the size of a spinlock but it changes locking to a potentially less optimal trylock. Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a __raw_spin_is_contended that uses the lock data itself to determine whether there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is not set. Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to decouple it from the spinlock implementation, and make it typesafe (rwlocks do not have any need_lockbreak sites -- why do they even get bloated up with that break_lock then?). Signed-off-by: Nick Piggin Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- include/linux/sched.h | 21 +++++++-------------- include/linux/spinlock.h | 6 ++++++ include/linux/spinlock_types.h | 4 ++-- include/linux/spinlock_up.h | 2 ++ 4 files changed, 17 insertions(+), 16 deletions(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 2d0546e884ea..9d4797609aa5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1922,23 +1922,16 @@ extern int cond_resched_softirq(void); /* * Does a critical section need to be broken due to another - * task waiting?: + * task waiting?: (technically does not depend on CONFIG_PREEMPT, + * but a general need for low latency) */ -#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP) -# define need_lockbreak(lock) ((lock)->break_lock) -#else -# define need_lockbreak(lock) 0 -#endif - -/* - * Does a critical section need to be broken due to another - * task waiting or preemption being signalled: - */ -static inline int lock_need_resched(spinlock_t *lock) +static inline int spin_needbreak(spinlock_t *lock) { - if (need_lockbreak(lock) || need_resched()) - return 1; +#ifdef CONFIG_PREEMPT + return spin_is_contended(lock); +#else return 0; +#endif } /* diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index c376f3b36c89..124449733c55 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -120,6 +120,12 @@ do { \ #define spin_is_locked(lock) __raw_spin_is_locked(&(lock)->raw_lock) +#ifdef CONFIG_GENERIC_LOCKBREAK +#define spin_is_contended(lock) ((lock)->break_lock) +#else +#define spin_is_contended(lock) __raw_spin_is_contended(&(lock)->raw_lock) +#endif + /** * spin_unlock_wait - wait until the spinlock gets unlocked * @lock: the spinlock in question. diff --git a/include/linux/spinlock_types.h b/include/linux/spinlock_types.h index f6a3a951b79e..68d88f71f1a2 100644 --- a/include/linux/spinlock_types.h +++ b/include/linux/spinlock_types.h @@ -19,7 +19,7 @@ typedef struct { raw_spinlock_t raw_lock; -#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP) +#ifdef CONFIG_GENERIC_LOCKBREAK unsigned int break_lock; #endif #ifdef CONFIG_DEBUG_SPINLOCK @@ -35,7 +35,7 @@ typedef struct { typedef struct { raw_rwlock_t raw_lock; -#if defined(CONFIG_PREEMPT) && defined(CONFIG_SMP) +#ifdef CONFIG_GENERIC_LOCKBREAK unsigned int break_lock; #endif #ifdef CONFIG_DEBUG_SPINLOCK diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h index ea54c4c9a4ec..938234c4a996 100644 --- a/include/linux/spinlock_up.h +++ b/include/linux/spinlock_up.h @@ -64,6 +64,8 @@ static inline void __raw_spin_unlock(raw_spinlock_t *lock) # define __raw_spin_trylock(lock) ({ (void)(lock); 1; }) #endif /* DEBUG_SPINLOCK */ +#define __raw_spin_is_contended(lock) (((void)(lock), 0)) + #define __raw_read_can_lock(lock) (((void)(lock), 1)) #define __raw_write_can_lock(lock) (((void)(lock), 1)) -- cgit v1.2.2