user/pingpong.c

   1 // Ping-pong a counter between two processes.
   2 // Only need to start one of these -- splits into two with fork.
   3
   4 #include <inc/lib.h>
   5
   6 void
   7 umain(void)
   8 {
   9         envid_t who;
  10
  11         if ((who = fork()) != 0) {
  12                 // get the ball rolling
  13                 cprintf("send 0 from %x to %x\n", sys_getenvid(), who);
  14                 ipc_send(who, 0, 0, 0);
  15         }
  16
  17         while (1) {
  18                 uint32_t i = ipc_recv(&who, 0, 0);
  19                 cprintf("%x got %d from %x\n", sys_getenvid(), i, who);
  20                 if (i == 10)
  21                         return;
  22                 i++;
  23                 ipc_send(who, i, 0, 0);
  24                 if (i == 10)
  25                         return;
  26         }
  27
  28 }
  29