i386/junos/ucla/src/lab3/kern/sched.c

   1 #include <inc/assert.h>
   2
   3 #include <kern/env.h>
   4 #include <kern/pmap.h>
   5 #include <kern/monitor.h>
   6
   7 // Choose a user environment to run and run it.
   8 void
   9 sched_yield(void)
  10 {
  11         // Implement simple round-robin scheduling.
  12         // Search through 'envs' for a runnable environment,
  13         // in circular fashion starting after the previously running env,
  14         // and switch to the first such environment found.
  15         // It's OK to choose the previously running env if no other env
  16         // is runnable.
  17
  18         // LAB 3: Your code here.
  19
  20         // Run the special idle environment when nothing else is runnable.
  21         if (envs[0].env_status == ENV_RUNNABLE)
  22                 env_run(&envs[0]);
  23         else {
  24                 cprintf("Idle loop - nothing more to do!\n");
  25                 while (1)
  26                         monitor(NULL);
  27         }
  28 }