diff options
Diffstat (limited to 'include/asm-generic/qrwlock.h')
| -rw-r--r-- | include/asm-generic/qrwlock.h | 63 |
1 files changed, 40 insertions, 23 deletions
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h index 3aefde23dcea..75b8f4601b28 100644 --- a/include/asm-generic/qrwlock.h +++ b/include/asm-generic/qrwlock.h @@ -2,6 +2,10 @@ /* * Queue read/write lock * + * These use generic atomic and locking routines, but depend on a fair spinlock + * implementation in order to be fair themselves. The implementation in + * asm-generic/spinlock.h meets these requirements. + * * (C) Copyright 2013-2014 Hewlett-Packard Development Company, L.P. * * Authors: Waiman Long <waiman.long@hp.com> @@ -15,6 +19,8 @@ #include <asm-generic/qrwlock_types.h> +/* Must be included from asm/spinlock.h after defining arch_spin_is_locked. */ + /* * Writer states & reader shift and bias. */ @@ -31,13 +37,13 @@ extern void queued_read_lock_slowpath(struct qrwlock *lock); extern void queued_write_lock_slowpath(struct qrwlock *lock); /** - * queued_read_trylock - try to acquire read lock of a queue rwlock - * @lock : Pointer to queue rwlock structure + * queued_read_trylock - try to acquire read lock of a queued rwlock + * @lock : Pointer to queued rwlock structure * Return: 1 if lock acquired, 0 if failed */ static inline int queued_read_trylock(struct qrwlock *lock) { - u32 cnts; + int cnts; cnts = atomic_read(&lock->cnts); if (likely(!(cnts & _QW_WMASK))) { @@ -50,13 +56,13 @@ static inline int queued_read_trylock(struct qrwlock *lock) } /** - * queued_write_trylock - try to acquire write lock of a queue rwlock - * @lock : Pointer to queue rwlock structure + * queued_write_trylock - try to acquire write lock of a queued rwlock + * @lock : Pointer to queued rwlock structure * Return: 1 if lock acquired, 0 if failed */ static inline int queued_write_trylock(struct qrwlock *lock) { - u32 cnts; + int cnts; cnts = atomic_read(&lock->cnts); if (unlikely(cnts)) @@ -66,12 +72,12 @@ static inline int queued_write_trylock(struct qrwlock *lock) _QW_LOCKED)); } /** - * queued_read_lock - acquire read lock of a queue rwlock - * @lock: Pointer to queue rwlock structure + * queued_read_lock - acquire read lock of a queued rwlock + * @lock: Pointer to queued rwlock structure */ static inline void queued_read_lock(struct qrwlock *lock) { - u32 cnts; + int cnts; cnts = atomic_add_return_acquire(_QR_BIAS, &lock->cnts); if (likely(!(cnts & _QW_WMASK))) @@ -82,12 +88,12 @@ static inline void queued_read_lock(struct qrwlock *lock) } /** - * queued_write_lock - acquire write lock of a queue rwlock - * @lock : Pointer to queue rwlock structure + * queued_write_lock - acquire write lock of a queued rwlock + * @lock : Pointer to queued rwlock structure */ static inline void queued_write_lock(struct qrwlock *lock) { - u32 cnts = 0; + int cnts = 0; /* Optimize for the unfair lock case where the fair flag is 0. */ if (likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED))) return; @@ -96,8 +102,8 @@ static inline void queued_write_lock(struct qrwlock *lock) } /** - * queued_read_unlock - release read lock of a queue rwlock - * @lock : Pointer to queue rwlock structure + * queued_read_unlock - release read lock of a queued rwlock + * @lock : Pointer to queued rwlock structure */ static inline void queued_read_unlock(struct qrwlock *lock) { @@ -108,23 +114,34 @@ static inline void queued_read_unlock(struct qrwlock *lock) } /** - * queued_write_unlock - release write lock of a queue rwlock - * @lock : Pointer to queue rwlock structure + * queued_write_unlock - release write lock of a queued rwlock + * @lock : Pointer to queued rwlock structure */ static inline void queued_write_unlock(struct qrwlock *lock) { smp_store_release(&lock->wlocked, 0); } +/** + * queued_rwlock_is_contended - check if the lock is contended + * @lock : Pointer to queued rwlock structure + * Return: 1 if lock contended, 0 otherwise + */ +static inline int queued_rwlock_is_contended(struct qrwlock *lock) +{ + return arch_spin_is_locked(&lock->wait_lock); +} + /* * Remapping rwlock architecture specific functions to the corresponding - * queue rwlock functions. + * queued rwlock functions. */ -#define arch_read_lock(l) queued_read_lock(l) -#define arch_write_lock(l) queued_write_lock(l) -#define arch_read_trylock(l) queued_read_trylock(l) -#define arch_write_trylock(l) queued_write_trylock(l) -#define arch_read_unlock(l) queued_read_unlock(l) -#define arch_write_unlock(l) queued_write_unlock(l) +#define arch_read_lock(l) queued_read_lock(l) +#define arch_write_lock(l) queued_write_lock(l) +#define arch_read_trylock(l) queued_read_trylock(l) +#define arch_write_trylock(l) queued_write_trylock(l) +#define arch_read_unlock(l) queued_read_unlock(l) +#define arch_write_unlock(l) queued_write_unlock(l) +#define arch_rwlock_is_contended(l) queued_rwlock_is_contended(l) #endif /* __ASM_GENERIC_QRWLOCK_H */ |