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

1.1       root        1: /* resched.c  -  resched */
                      2: 
                      3: #include <conf.h>
                      4: #include <kernel.h>
                      5: #include <proc.h>
                      6: #include <q.h>
                      7: 
                      8: /*------------------------------------------------------------------------
                      9:  * resched  --  reschedule processor to highest priority ready process
                     10:  *
                     11:  * Notes:      Upon entry, currpid gives current process id.
                     12:  *             Proctab[currpid].pstate gives correct NEXT state for
                     13:  *                     current process if other than PRCURR.
                     14:  *------------------------------------------------------------------------
                     15:  */
                     16: int    resched()
                     17: {
                     18:        register struct pentry  *optr;  /* pointer to old process entry */
                     19:        register struct pentry  *nptr;  /* pointer to new process entry */
                     20: 
                     21:        /* no switch needed if current process priority higher than next*/
                     22: 
                     23:        if ( ( (optr= &proctab[currpid])->pstate == PRCURR) &&
                     24:           (lastkey(rdytail)<optr->pprio))
                     25:                return(OK);
                     26: 
                     27:        /* force context switch */
                     28: 
                     29:        if (optr->pstate == PRCURR) {
                     30:                optr->pstate = PRREADY;
                     31:                insert(currpid,rdyhead,optr->pprio);
                     32:        }
                     33: 
                     34:        /* remove highest priority process at end of ready list */
                     35: 
                     36:        nptr = &proctab[ (currpid = getlast(rdytail)) ];
                     37:        nptr->pstate = PRCURR;          /* mark it currently running    */
                     38: #ifdef STKCHK
                     39:        if ( *( (int *)nptr->pbase  ) != MAGIC ) {
                     40:                kprintf("Bad magic pid=%d, value=%x, at %x\n",
                     41:                        currpid, *( (int *)nptr->pbase ), nptr->pbase);
                     42:                panic("stack corrupted");
                     43:        }
                     44:        if ( ((unsigned)nptr->pregs[SPINDX]) < ((unsigned)nptr->plimit) ) {
                     45:                kprintf("Bad SP pid=%d (%s), lim=%x will be %x\n",
                     46:                        currpid, nptr->pname, nptr->plimit,
                     47:                        nptr->pregs[SPINDX]);
                     48:                panic("stack overflow");
                     49:        }
                     50: #endif
                     51: #ifdef RTCLOCK
                     52:        preempt = QUANTUM;              /* reset preemption counter     */
                     53: #endif
                     54:        ctxsw(nptr->pregs);
                     55:        return(OK);
                     56: }

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