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author | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
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committer | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
commit | 57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch) | |
tree | 5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/sparc/include/asm/rwsem.h |
Initial import
Diffstat (limited to 'arch/sparc/include/asm/rwsem.h')
-rw-r--r-- | arch/sparc/include/asm/rwsem.h | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/arch/sparc/include/asm/rwsem.h b/arch/sparc/include/asm/rwsem.h new file mode 100644 index 000000000..069bf4d66 --- /dev/null +++ b/arch/sparc/include/asm/rwsem.h @@ -0,0 +1,124 @@ +/* + * rwsem.h: R/W semaphores implemented using CAS + * + * Written by David S. Miller (davem@redhat.com), 2001. + * Derived from asm-i386/rwsem.h + */ +#ifndef _SPARC64_RWSEM_H +#define _SPARC64_RWSEM_H + +#ifndef _LINUX_RWSEM_H +#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead" +#endif + +#ifdef __KERNEL__ + +#define RWSEM_UNLOCKED_VALUE 0x00000000L +#define RWSEM_ACTIVE_BIAS 0x00000001L +#define RWSEM_ACTIVE_MASK 0xffffffffL +#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1) +#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS +#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) + +/* + * lock for reading + */ +static inline void __down_read(struct rw_semaphore *sem) +{ + if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L)) + rwsem_down_read_failed(sem); +} + +static inline int __down_read_trylock(struct rw_semaphore *sem) +{ + long tmp; + + while ((tmp = sem->count) >= 0L) { + if (tmp == cmpxchg(&sem->count, tmp, + tmp + RWSEM_ACTIVE_READ_BIAS)) { + return 1; + } + } + return 0; +} + +/* + * lock for writing + */ +static inline void __down_write_nested(struct rw_semaphore *sem, int subclass) +{ + long tmp; + + tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS, + (atomic64_t *)(&sem->count)); + if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) + rwsem_down_write_failed(sem); +} + +static inline void __down_write(struct rw_semaphore *sem) +{ + __down_write_nested(sem, 0); +} + +static inline int __down_write_trylock(struct rw_semaphore *sem) +{ + long tmp; + + tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, + RWSEM_ACTIVE_WRITE_BIAS); + return tmp == RWSEM_UNLOCKED_VALUE; +} + +/* + * unlock after reading + */ +static inline void __up_read(struct rw_semaphore *sem) +{ + long tmp; + + tmp = atomic64_dec_return((atomic64_t *)(&sem->count)); + if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L)) + rwsem_wake(sem); +} + +/* + * unlock after writing + */ +static inline void __up_write(struct rw_semaphore *sem) +{ + if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS, + (atomic64_t *)(&sem->count)) < 0L)) + rwsem_wake(sem); +} + +/* + * implement atomic add functionality + */ +static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem) +{ + atomic64_add(delta, (atomic64_t *)(&sem->count)); +} + +/* + * downgrade write lock to read lock + */ +static inline void __downgrade_write(struct rw_semaphore *sem) +{ + long tmp; + + tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count)); + if (tmp < 0L) + rwsem_downgrade_wake(sem); +} + +/* + * implement exchange and add functionality + */ +static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem) +{ + return atomic64_add_return(delta, (atomic64_t *)(&sem->count)); +} + +#endif /* __KERNEL__ */ + +#endif /* _SPARC64_RWSEM_H */ |