101 lines
2.5 KiB
C
101 lines
2.5 KiB
C
/* $Id: rwsem.h,v 1.5 2001/11/18 00:12:56 davem Exp $
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* rwsem.h: R/W semaphores implemented using CAS
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*
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* Written by David S. Miller (davem@redhat.com), 2001.
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* Derived from asm-i386/rwsem.h
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*/
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#ifndef _SPARC64_RWSEM_H
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#define _SPARC64_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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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <asm/rwsem-const.h>
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struct rwsem_waiter;
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struct rw_semaphore {
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signed int count;
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spinlock_t wait_lock;
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struct list_head wait_list;
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};
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#define __RWSEM_INITIALIZER(name) \
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{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) }
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#define DECLARE_RWSEM(name) \
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struct rw_semaphore name = __RWSEM_INITIALIZER(name)
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static __inline__ void init_rwsem(struct rw_semaphore *sem)
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{
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sem->count = RWSEM_UNLOCKED_VALUE;
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spin_lock_init(&sem->wait_lock);
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INIT_LIST_HEAD(&sem->wait_list);
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}
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extern void __down_read(struct rw_semaphore *sem);
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extern int __down_read_trylock(struct rw_semaphore *sem);
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extern void __down_write(struct rw_semaphore *sem);
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extern int __down_write_trylock(struct rw_semaphore *sem);
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extern void __up_read(struct rw_semaphore *sem);
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extern void __up_write(struct rw_semaphore *sem);
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extern void __downgrade_write(struct rw_semaphore *sem);
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static __inline__ int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
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{
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int tmp = delta;
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__asm__ __volatile__(
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"1:\tlduw [%2], %%g1\n\t"
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"add %%g1, %1, %%g7\n\t"
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"cas [%2], %%g1, %%g7\n\t"
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"cmp %%g1, %%g7\n\t"
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"bne,pn %%icc, 1b\n\t"
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" membar #StoreLoad | #StoreStore\n\t"
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"mov %%g7, %0\n\t"
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: "=&r" (tmp)
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: "0" (tmp), "r" (sem)
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: "g1", "g7", "memory", "cc");
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return tmp + delta;
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}
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#define rwsem_atomic_add rwsem_atomic_update
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static __inline__ __u16 rwsem_cmpxchgw(struct rw_semaphore *sem, __u16 __old, __u16 __new)
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{
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u32 old = (sem->count & 0xffff0000) | (u32) __old;
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u32 new = (old & 0xffff0000) | (u32) __new;
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u32 prev;
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again:
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__asm__ __volatile__("cas [%2], %3, %0\n\t"
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"membar #StoreLoad | #StoreStore"
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: "=&r" (prev)
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: "0" (new), "r" (sem), "r" (old)
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: "memory");
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/* To give the same semantics as x86 cmpxchgw, keep trying
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* if only the upper 16-bits changed.
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*/
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if (prev != old &&
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((prev & 0xffff) == (old & 0xffff)))
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goto again;
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return prev & 0xffff;
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}
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static __inline__ signed long rwsem_cmpxchg(struct rw_semaphore *sem, signed long old, signed long new)
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{
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return cmpxchg(&sem->count,old,new);
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}
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#endif /* __KERNEL__ */
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#endif /* _SPARC64_RWSEM_H */
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