nit in comment

ccd980be · Frans Kaashoek · 074ac7cc · ccd980be
--- a/proc.c
+++ b/proc.c
@@ -116,7 +116,7 @@ found:
  p->pid = nextpid++;
  release(&ptable.lock);

-  // Allocate kernel stack if necessary.
+  // Allocate kernel stack if possible.
  if((p->kstack = kalloc(KSTACKSIZE)) == 0){
    p->state = UNUSED;
    return 0;