user/idle.c

   1 // idle loop
   2
   3 #include <inc/x86.h>
   4 #include <inc/lib.h>
   5
   6 void
   7 umain(void)
   8 {
   9         binaryname = "idle";
  10
  11         // Loop forever, simply trying to yield to a different environment.
  12         // Instead of busy-waiting like this,
  13         // a better way would be to use the processor's HLT instruction
  14         // to cause the processor to stop executing until the next interrupt -
  15         // doing so allows the processor to conserve power more effectively.
  16         while (1) {
  17                 sys_yield();
  18
  19                 // Break into the JOS kernel monitor after each sys_yield().
  20                 // A real, "production" OS of course would NOT do this -
  21                 // it would just endlessly loop waiting for hardware interrupts
  22                 // to cause other environments to become runnable.
  23                 // However, in JOS it is easier for testing and grading
  24                 // if we invoke the kernel monitor after each iteration,
  25                 // because the first invocation of the idle environment
  26                 // usually means everything else has run to completion.
  27                 breakpoint();
  28         }
  29 }
  30