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Annotation of xinu/sys/wait.c, revision 1.1.1.1

1.1       root        1: /* wait.c - wait */
                      2: 
                      3: #include <conf.h>
                      4: #include <kernel.h>
                      5: #include <proc.h>
                      6: #include <q.h>
                      7: #include <sem.h>
                      8: 
                      9: /*------------------------------------------------------------------------
                     10:  * wait  --  make current process wait on a semaphore
                     11:  *------------------------------------------------------------------------
                     12:  */
                     13: SYSCALL        wait(sem)
                     14:        int     sem;
                     15: {
                     16:        PStype  ps;
                     17:        register struct sentry  *sptr;
                     18:        register struct pentry  *pptr;
                     19: 
                     20:        disable(ps);
                     21:        if (isbadsem(sem) || (sptr= &semaph[sem])->sstate==SFREE) {
                     22:                restore(ps);
                     23:                return(SYSERR);
                     24:        }
                     25:        if (--(sptr->semcnt) < 0) {
                     26:                (pptr = &proctab[currpid])->pstate = PRWAIT;
                     27:                pptr->psem = sem;
                     28:                enqueue(currpid,sptr->sqtail);
                     29:                resched();
                     30:        }
                     31:        restore(ps);
                     32:        return(OK);
                     33: }

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