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#include "u.h"
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#include "lib.h"
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#include "dat.h"
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#include "fns.h"
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#include "error.h"
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void
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rlock(RWlock *l)
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{
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	qlock(&l->x);		/* wait here for writers and exclusion */
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	lock(&l->lk);
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	l->readers++;
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	canqlock(&l->k);	/* block writers if we are the first reader */
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	unlock(&l->lk);
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	qunlock(&l->x);
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}
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void
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runlock(RWlock *l)
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{
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	lock(&l->lk);
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	if(--l->readers == 0)	/* last reader out allows writers */
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		qunlock(&l->k);
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	unlock(&l->lk);
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}
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void
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wlock(RWlock *l)
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{
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	qlock(&l->x);		/* wait here for writers and exclusion */
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	qlock(&l->k);		/* wait here for last reader */
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}
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void
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wunlock(RWlock *l)
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{
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	qunlock(&l->k);
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	qunlock(&l->x);
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}