xinu: Desktop/xinu_mips-1.0.2.tar/xinu_mips-1.0.2/system/resched.c Source File

00001 
00007 /* Embedded XINU, Copyright (C) 2007.  All rights reserved. */
00008 
00009 #include <kernel.h>
00010 #include <proc.h>
00011 #include <clock.h>
00012 #include <queue.h>
00013 
00014 extern void ctxsw(void *, void *);
00021 syscall resched(void)
00022 {
00023         pcb *oldproc;   /* pointer to old process entry */
00024         pcb *newproc;   /* pointer to new process entry */
00025 
00026         oldproc = &proctab[ currpid ];
00027 
00028         oldproc->irqstate = disable();
00029 
00030         /* place current process at end of ready queue */
00031         if (PRCURR == oldproc->state) 
00032         {
00033                 oldproc->state = PRREADY;
00034                 insert(currpid, readylist, oldproc->prio);
00035         }
00036 
00037         /* remove highest priority process in ready queue */
00038         currpid = dequeue(readylist);
00039         newproc = &proctab[ currpid ];
00040         newproc->state = PRCURR;        /* mark it currently running    */
00041 #ifdef  RTCLOCK
00042         preempt = QUANTUM;          /* reset preemption counter     */
00043 #endif
00044 
00045         ctxsw(&oldproc->stkptr, &newproc->stkptr);
00046 
00047         /* The OLD process returns here when resumed. */
00048         restore(oldproc->irqstate);
00049         return OK;
00050 }