174 lines
4.0 KiB
C
174 lines
4.0 KiB
C
#ifndef _ASM_POWERPC_RWSEM_H
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#define _ASM_POWERPC_RWSEM_H
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#ifndef _LINUX_RWSEM_H
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#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
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#endif
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#ifdef __KERNEL__
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/*
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* R/W semaphores for PPC using the stuff in lib/rwsem.c.
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* Adapted largely from include/asm-i386/rwsem.h
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* by Paul Mackerras <paulus@samba.org>.
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*/
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <asm/atomic.h>
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#include <asm/system.h>
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/*
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* the semaphore definition
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*/
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struct rw_semaphore {
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/* XXX this should be able to be an atomic_t -- paulus */
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signed int count;
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#define RWSEM_UNLOCKED_VALUE 0x00000000
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#define RWSEM_ACTIVE_BIAS 0x00000001
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#define RWSEM_ACTIVE_MASK 0x0000ffff
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#define RWSEM_WAITING_BIAS (-0x00010000)
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#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
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#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
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spinlock_t wait_lock;
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struct list_head wait_list;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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};
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
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#else
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# define __RWSEM_DEP_MAP_INIT(lockname)
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#endif
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#define __RWSEM_INITIALIZER(name) \
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{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
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LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
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#define DECLARE_RWSEM(name) \
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struct rw_semaphore name = __RWSEM_INITIALIZER(name)
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extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
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extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
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extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
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extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
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extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
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struct lock_class_key *key);
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#define init_rwsem(sem) \
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do { \
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static struct lock_class_key __key; \
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\
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__init_rwsem((sem), #sem, &__key); \
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} while (0)
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/*
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* lock for reading
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*/
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static inline void __down_read(struct rw_semaphore *sem)
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{
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if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
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rwsem_down_read_failed(sem);
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}
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static inline int __down_read_trylock(struct rw_semaphore *sem)
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{
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int tmp;
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while ((tmp = sem->count) >= 0) {
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if (tmp == cmpxchg(&sem->count, tmp,
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tmp + RWSEM_ACTIVE_READ_BIAS)) {
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return 1;
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}
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}
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return 0;
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}
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/*
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* lock for writing
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*/
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static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
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{
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int tmp;
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tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
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(atomic_t *)(&sem->count));
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if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
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rwsem_down_write_failed(sem);
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}
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static inline void __down_write(struct rw_semaphore *sem)
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{
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__down_write_nested(sem, 0);
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}
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static inline int __down_write_trylock(struct rw_semaphore *sem)
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{
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int tmp;
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tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
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RWSEM_ACTIVE_WRITE_BIAS);
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return tmp == RWSEM_UNLOCKED_VALUE;
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}
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/*
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* unlock after reading
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*/
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static inline void __up_read(struct rw_semaphore *sem)
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{
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int tmp;
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tmp = atomic_dec_return((atomic_t *)(&sem->count));
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if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
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rwsem_wake(sem);
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}
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/*
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* unlock after writing
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*/
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static inline void __up_write(struct rw_semaphore *sem)
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{
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if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
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(atomic_t *)(&sem->count)) < 0))
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rwsem_wake(sem);
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}
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/*
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* implement atomic add functionality
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*/
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static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
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{
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atomic_add(delta, (atomic_t *)(&sem->count));
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}
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/*
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* downgrade write lock to read lock
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*/
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static inline void __downgrade_write(struct rw_semaphore *sem)
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{
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int tmp;
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tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
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if (tmp < 0)
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rwsem_downgrade_wake(sem);
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}
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/*
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* implement exchange and add functionality
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*/
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static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
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{
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return atomic_add_return(delta, (atomic_t *)(&sem->count));
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}
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static inline int rwsem_is_locked(struct rw_semaphore *sem)
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{
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return (sem->count != 0);
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}
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_RWSEM_H */
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