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130 lines
3.1 KiB
130 lines
3.1 KiB
#ifndef _ASM_GENERIC_RWSEM_H |
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#define _ASM_GENERIC_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 originally 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 <[email protected]>. |
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*/ |
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/* |
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* the semaphore definition |
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*/ |
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#ifdef CONFIG_64BIT |
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# define RWSEM_ACTIVE_MASK 0xffffffffL |
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#else |
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# define RWSEM_ACTIVE_MASK 0x0000ffffL |
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#endif |
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#define RWSEM_UNLOCKED_VALUE 0x00000000L |
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#define RWSEM_ACTIVE_BIAS 0x00000001L |
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#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1) |
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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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/* |
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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_long_inc_return_acquire((atomic_long_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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long tmp; |
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while ((tmp = atomic_long_read(&sem->count)) >= 0) { |
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if (tmp == atomic_long_cmpxchg_acquire(&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(struct rw_semaphore *sem) |
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{ |
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long tmp; |
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tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, |
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(atomic_long_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 int __down_write_killable(struct rw_semaphore *sem) |
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{ |
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long tmp; |
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tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, |
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(atomic_long_t *)&sem->count); |
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if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) |
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if (IS_ERR(rwsem_down_write_failed_killable(sem))) |
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return -EINTR; |
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return 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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long tmp; |
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tmp = atomic_long_cmpxchg_acquire(&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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long tmp; |
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tmp = atomic_long_dec_return_release((atomic_long_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_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, |
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(atomic_long_t *)&sem->count) < 0)) |
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rwsem_wake(sem); |
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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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long tmp; |
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/* |
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* When downgrading from exclusive to shared ownership, |
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* anything inside the write-locked region cannot leak |
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* into the read side. In contrast, anything in the |
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* read-locked region is ok to be re-ordered into the |
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* write side. As such, rely on RELEASE semantics. |
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*/ |
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tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, |
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(atomic_long_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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#endif /* __KERNEL__ */ |
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#endif /* _ASM_GENERIC_RWSEM_H */
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