i386/junos/ucla/src/lab5/user/pingpongs.c

   1 // Ping-pong a counter between two shared-memory processes.
   2 // Only need to start one of these -- splits into two with sfork.
   3
   4 #include <inc/lib.h>
   5
   6 uint32_t val;
   7
   8 asmlinkage void
   9 umain(int argc, char **argv)
  10 {
  11         envid_t who;
  12         uint32_t i;
  13
  14         i = 0;
  15         if ((who = sfork()) != 0) {
  16                 cprintf("i am %08x; env is %p\n", sys_getenvid(), thisenv);
  17                 // get the ball rolling
  18                 cprintf("send 0 from %x to %x\n", sys_getenvid(), who);
  19                 ipc_send(who, 0, 0, 0);
  20         }
  21
  22         while (1) {
  23                 ipc_recv(&who, 0, 0);
  24                 cprintf("%x got %d from %x (env is %p %x)\n", sys_getenvid(), val, who, thisenv, thisenv->env_id);
  25                 if (val == 10)
  26                         return;
  27                 ++val;
  28                 ipc_send(who, 0, 0, 0);
  29                 if (val == 10)
  30                         return;
  31         }
  32
  33 }