40 lines
634 B
C
40 lines
634 B
C
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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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}
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