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Diffstat (limited to 'include/asm-xtensa/rwsem.h')
| -rw-r--r-- | include/asm-xtensa/rwsem.h | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/include/asm-xtensa/rwsem.h b/include/asm-xtensa/rwsem.h new file mode 100644 index 00000000000..3c02b0e033f --- /dev/null +++ b/include/asm-xtensa/rwsem.h @@ -0,0 +1,175 @@ +/* + * include/asm-xtensa/rwsem.h + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Largely copied from include/asm-ppc/rwsem.h + * + * Copyright (C) 2001 - 2005 Tensilica Inc. + */ + +#ifndef _XTENSA_RWSEM_H +#define _XTENSA_RWSEM_H + +#include <linux/list.h> +#include <linux/spinlock.h> +#include <asm/atomic.h> +#include <asm/system.h> + +/* + * the semaphore definition + */ +struct rw_semaphore { + signed long count; +#define RWSEM_UNLOCKED_VALUE 0x00000000 +#define RWSEM_ACTIVE_BIAS 0x00000001 +#define RWSEM_ACTIVE_MASK 0x0000ffff +#define RWSEM_WAITING_BIAS (-0x00010000) +#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS +#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) + spinlock_t wait_lock; + struct list_head wait_list; +#if RWSEM_DEBUG + int debug; +#endif +}; + +/* + * initialisation + */ +#if RWSEM_DEBUG +#define __RWSEM_DEBUG_INIT , 0 +#else +#define __RWSEM_DEBUG_INIT /* */ +#endif + +#define __RWSEM_INITIALIZER(name) \ + { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ + LIST_HEAD_INIT((name).wait_list) \ + __RWSEM_DEBUG_INIT } + +#define DECLARE_RWSEM(name) \ + struct rw_semaphore name = __RWSEM_INITIALIZER(name) + +extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); +extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); +extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); +extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); + +static inline void init_rwsem(struct rw_semaphore *sem) +{ + sem->count = RWSEM_UNLOCKED_VALUE; + spin_lock_init(&sem->wait_lock); + INIT_LIST_HEAD(&sem->wait_list); +#if RWSEM_DEBUG + sem->debug = 0; +#endif +} + +/* + * lock for reading + */ +static inline void __down_read(struct rw_semaphore *sem) +{ + if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0) + smp_wmb(); + else + rwsem_down_read_failed(sem); +} + +static inline int __down_read_trylock(struct rw_semaphore *sem) +{ + int tmp; + + while ((tmp = sem->count) >= 0) { + if (tmp == cmpxchg(&sem->count, tmp, + tmp + RWSEM_ACTIVE_READ_BIAS)) { + smp_wmb(); + return 1; + } + } + return 0; +} + +/* + * lock for writing + */ +static inline void __down_write(struct rw_semaphore *sem) +{ + int tmp; + + tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS, + (atomic_t *)(&sem->count)); + if (tmp == RWSEM_ACTIVE_WRITE_BIAS) + smp_wmb(); + else + rwsem_down_write_failed(sem); +} + +static inline int __down_write_trylock(struct rw_semaphore *sem) +{ + int tmp; + + tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE, + RWSEM_ACTIVE_WRITE_BIAS); + smp_wmb(); + return tmp == RWSEM_UNLOCKED_VALUE; +} + +/* + * unlock after reading + */ +static inline void __up_read(struct rw_semaphore *sem) +{ + int tmp; + + smp_wmb(); + tmp = atomic_sub_return(1,(atomic_t *)(&sem->count)); + if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0) + rwsem_wake(sem); +} + +/* + * unlock after writing + */ +static inline void __up_write(struct rw_semaphore *sem) +{ + smp_wmb(); + if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS, + (atomic_t *)(&sem->count)) < 0) + rwsem_wake(sem); +} + +/* + * implement atomic add functionality + */ +static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem) +{ + atomic_add(delta, (atomic_t *)(&sem->count)); +} + +/* + * downgrade write lock to read lock + */ +static inline void __downgrade_write(struct rw_semaphore *sem) +{ + int tmp; + + smp_wmb(); + tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count)); + if (tmp < 0) + rwsem_downgrade_wake(sem); +} + +/* + * implement exchange and add functionality + */ +static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) +{ + smp_mb(); + return atomic_add_return(delta, (atomic_t *)(&sem->count)); +} + +#endif /* _XTENSA_RWSEM_XADD_H */ |