54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/*
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* Copyright (C) 2015 Giacomo Tesio <giacomo@tesio.it>
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*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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#include <u.h>
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#include <libc.h>
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void
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jehanne_lock(Lock *l)
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{
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if(jehanne_ainc(&l->key) == 1)
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return; /* changed from 0 -> 1: we hold lock */
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/* otherwise wait in kernel */
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while(sys_semacquire(&l->sem, 1) < 0){
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/* interrupted; try again */
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}
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}
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void
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jehanne_unlock(Lock *l)
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{
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if(jehanne_adec(&l->key) == 0)
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return; /* changed from 1 -> 0: no contention */
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sys_semrelease(&l->sem, 1);
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}
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int
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jehanne_canlock(Lock *l)
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{
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if(jehanne_ainc(&l->key) == 1)
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return 1; /* changed from 0 -> 1: success */
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/* Undo increment (but don't miss wakeup) */
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if(jehanne_adec(&l->key) == 0)
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return 0; /* changed from 1 -> 0: no contention */
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sys_semrelease(&l->sem, 1);
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return 0;
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}
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int
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jehanne_lockt(Lock *l, uint32_t ms)
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{
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if(jehanne_ainc(&l->key) == 1)
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return 1; /* changed from 0 -> 1: we hold lock */
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/* otherwise wait in kernel */
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return jehanne_tsemacquire(&l->sem, ms);
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}
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