From 20fa5aa70d2a5e599ea2604f51baa49c6e891ab3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustav=20S=C3=B6rn=C3=A4s?= <gustav@sornas.net>
Date: Sun, 14 Mar 2021 13:28:01 +0100
Subject: check all pointers before dereferencing

---
 src/userprog/process.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'src/userprog/process.c')

diff --git a/src/userprog/process.c b/src/userprog/process.c
index fbf2f50..6170b53 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -145,6 +145,8 @@ process_wait (tid_t child_tid)
       sema_down (&pc->exit_sema);
       int exit_status = pc->exit_status;
       pc->exit_status = -1;
+      sema_up (&pc->exit_sema);  // a bit of a hack
+                                 // the child is killed so we can read again if we want to
       return exit_status;
     }
   }
-- 
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