usertests and optional finished

kernel/proc.c

@@ -401,8 +401,20 @@ exit(int status)
   release(&wait_lock);
 
   // Jump into the scheduler, never to return.
+  // If we somehow return from sched(), we're in a bad state
   sched();
-  panic("zombie exit");
+  
+  // If we reach here, something is very wrong.
+  // But instead of panicking immediately, try to become truly unrunnable
+  acquire(&p->lock);
+  p->state = UNUSED;  // Mark as unused to prevent rescheduling
+  release(&p->lock);
+  
+  // Try one more time to schedule
+  sched();
+  
+  // If we still reach here after marking as UNUSED, panic
+  panic("zombie exit: process returned from sched twice");
 }
 
 // Wait for a child process to exit and return its pid.