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When using x86 specific rwsem correctly intepret rwsem->count.

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This commit is contained in:
Brian Behlendorf 2009-12-01 15:47:27 -08:00
parent 4e5691faf6
commit 5652e7b497
1 changed files with 12 additions and 6 deletions
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18
include/sys/rwlock.h
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@ -47,9 +47,10 @@ typedef struct {
} krwlock_t;
/*
* For the generic and x86 implementations of rw-semaphores the following
* is true. If your semaphore implementation internally represents the
* semaphore state differently special case handling will be required.
* For the generic implementations of rw-semaphores the following is
* true. If your semaphore implementation internally represents the
* semaphore state differently. Then special case handling will be
* required so RW_COUNT() provides these semantics:
* - if activity/count is 0 then there are no active readers or writers
* - if activity/count is +ve then that is the number of active readers
* - if activity/count is -1 then there is one active writer
@ -63,9 +64,14 @@ typedef struct {
extern void __up_read_locked(struct rw_semaphore *);
extern int __down_write_trylock_locked(struct rw_semaphore *);
#else
# define RW_COUNT(rwp) (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
# define rw_exit_locked(rwp) up_read(rwp)
# define rw_tryenter_locked(rwp) down_write_trylock(rwp)
# ifdef _I386_RWSEM_H
# define RW_COUNT(rwp) ((SEM(rwp)->count < 0) ? (-1) : \
(SEM(rwp)->count & RWSEM_ACTIVE_MASK))
# else
# define RW_COUNT(rwp) (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
# endif
# define rw_exit_locked(rwp) up_read(rwp)
# define rw_tryenter_locked(rwp) down_write_trylock(rwp)
#endif
static inline kthread_t *