process: work on pre-emption - give it its own debug form

Also scribble over the p_page pointers of the dead process on exit so
we can catch that case

diff --git a/Kernel/process.c b/Kernel/process.c
index 9721c99..6b779a1 100644 (file)
--- a/Kernel/process.c
+++ b/Kernel/process.c
@@ -1,6 +1,7 @@
 #undef DEBUG                   /* turn this on to enable syscall tracing */
 #undef DEBUGHARDER             /* report calls to wakeup() that lead nowhere */
 #undef DEBUGREALLYHARD         /* turn on getproc dumping */
+#define DEBUG_PREEMPT          /* debug pre-emption */
 
 #include <kernel.h>
 #include <tty.h>
@@ -366,13 +367,16 @@ void timer_interrupt(void)
        /* Check run time of current process */
        if ((++runticks >= udata.u_ptab->p_priority)
            && !udata.u_insys && inint && nready > 1) { /* Time to switch out? */
-#ifdef DEBUG
-               kputs("[preempt]");
-               kprintf("Prio = %d\n", udata.u_ptab->p_priority);
+#ifdef DEBUG_PREEMPT
+               kprintf("[preempt %x %d]", udata.u_ptab,
+                       udata.u_ptab->p_priority);
 #endif
                udata.u_insys = true;
                udata.u_ptab->p_status = P_READY;
                switchout();
+#ifdef DEBUG_PREEMPT
+               kprintf("[preempt return %x]", udata.u_ptab);
+#endif
                udata.u_insys = false;  /* We have switched back in */
        }
 #endif
@@ -612,6 +616,8 @@ void doexit(int16_t val, int16_t val2)
 #ifdef CONFIG_ACCT
        acctexit(p);
 #endif
+        udata.u_page = 0xFFFFU;
+        udata.u_page2 = 0xFFFFU;
        /* FIXME: send SIGCLD here */
        /* FIXME: POSIX.1 says that SIG_IGN for SIGCLD means don't go
           zombie, just clean up as we go */