/* $Id: rwsem.h,v 1.5 2001/11/18 00:12:56 davem Exp $ * rwsem.h: R/W semaphores implemented using CAS * * Written by David S. Miller (davem@redhat.com), 2001. * Derived from asm-i386/rwsem.h */ #ifndef _SPARC64_RWSEM_H #define _SPARC64_RWSEM_H #ifndef _LINUX_RWSEM_H #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead" #endif #ifdef __KERNEL__ #include <linux/list.h> #include <linux/spinlock.h> #include <asm/rwsem-const.h> struct rwsem_waiter; struct rw_semaphore { signed int count; spinlock_t wait_lock; struct list_head wait_list; }; #define __RWSEM_INITIALIZER(name) \ { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) } #define DECLARE_RWSEM(name) \ struct rw_semaphore name = __RWSEM_INITIALIZER(name) 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); } extern void __down_read(struct rw_semaphore *sem); extern int __down_read_trylock(struct rw_semaphore *sem); extern void __down_write(struct rw_semaphore *sem); extern int __down_write_trylock(struct rw_semaphore *sem); extern void __up_read(struct rw_semaphore *sem); extern void __up_write(struct rw_semaphore *sem); extern void __downgrade_write(struct rw_semaphore *sem); static __inline__ int rwsem_atomic_update(int delta, struct rw_semaphore *sem) { int tmp = delta; __asm__ __volatile__( "1:\tlduw [%2], %%g1\n\t" "add %%g1, %1, %%g7\n\t" "cas [%2], %%g1, %%g7\n\t" "cmp %%g1, %%g7\n\t" "bne,pn %%icc, 1b\n\t" " membar #StoreLoad | #StoreStore\n\t" "mov %%g7, %0\n\t" : "=&r" (tmp) : "0" (tmp), "r" (sem) : "g1", "g7", "memory", "cc"); return tmp + delta; } #define rwsem_atomic_add rwsem_atomic_update static __inline__ __u16 rwsem_cmpxchgw(struct rw_semaphore *sem, __u16 __old, __u16 __new) { u32 old = (sem->count & 0xffff0000) | (u32) __old; u32 new = (old & 0xffff0000) | (u32) __new; u32 prev; again: __asm__ __volatile__("cas [%2], %3, %0\n\t" "membar #StoreLoad | #StoreStore" : "=&r" (prev) : "0" (new), "r" (sem), "r" (old) : "memory"); /* To give the same semantics as x86 cmpxchgw, keep trying * if only the upper 16-bits changed. */ if (prev != old && ((prev & 0xffff) == (old & 0xffff))) goto again; return prev & 0xffff; } static __inline__ signed long rwsem_cmpxchg(struct rw_semaphore *sem, signed long old, signed long new) { return cmpxchg(&sem->count,old,new); } #endif /* __KERNEL__ */ #endif /* _SPARC64_RWSEM_H */