more defensive programming

diff --git a/proc.c b/proc.c
index 8aa1ff155b349eb9f95733b33a85d62d34968f06..06ee2fd11b2bf0b6994dec027456edb0668a078e 100644 (file)
--- a/proc.c
+++ b/proc.c
@@ -371,7 +371,9 @@ proc_wait(void)
     havekids = 0;
     for(i = 0; i < NPROC; i++){
       p = &proc[i];
-      if(p->state != UNUSED && p->ppid == cp->pid){
+      if(p->state == UNUSED)
+        continue;
+      if(p->ppid == cp->pid){
         if(p->state == ZOMBIE){
           // Found one.
           kfree(p->mem, p->sz);
@@ -379,6 +381,7 @@ proc_wait(void)
           pid = p->pid;
           p->state = UNUSED;
           p->pid = 0;
+          p->ppid = 0;
           release(&proc_table_lock);
           return pid;
         }