From 5652e7b497256647cdcd4d5825cdb23b1b797dd0 Mon Sep 17 00:00:00 2001 From: Brian Behlendorf Date: Tue, 1 Dec 2009 15:47:27 -0800 Subject: [PATCH] When using x86 specific rwsem correctly intepret rwsem->count. --- include/sys/rwlock.h | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/include/sys/rwlock.h b/include/sys/rwlock.h index 75356b9..0043f39 100644 --- a/include/sys/rwlock.h +++ b/include/sys/rwlock.h @@ -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 * -- 2.39.2