parent waits for child to start

1 files changed, 11 insertions, 8 deletions

diff --git a/src/userprog/process.c b/src/userprog/process.c
index c0a770b..437d6c0 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -15,11 +15,15 @@
 #include "threads/init.h"
 #include "threads/interrupt.h"
 #include "threads/palloc.h"
+#include "threads/synch.h"
 #include "threads/thread.h"
 #include "threads/vaddr.h"
 
 struct start_process_args
   {
+    struct semaphore sema;
+
+    // parent -> child
     char *file_name;
   };
 
@@ -38,7 +42,7 @@ process_execute (const char *file_name)
 
   printf("%s starting %s\n", thread_current ()->name, file_name);
 
-  sema_init (&args.sema);
+  sema_init (&args.sema, 0);
 
   /* Make a copy of FILE_NAME.
      Otherwise there's a race between the caller and load(). */
@@ -54,13 +58,10 @@ process_execute (const char *file_name)
      wait for the child to signal that it has read the args. Only then can
      we free resources and return the tid. */
   tid = thread_create (file_name, PRI_DEFAULT, start_process, &args);
-  if (tid == TID_ERROR) {
-    palloc_free_page (args.file_name); 
-  } else {
-    //TODO thread created, wait to see if start_process worked
-    //     return -1 if failed
+  if (tid != TID_ERROR) {
+    sema_down (&args.sema);
   }
-  printf("woops\n");
+  palloc_free_page (args.file_name);
   return tid;
 }
 
@@ -81,14 +82,16 @@ start_process (void *args_)
   printf("reading\n");
   success = load (args->file_name, &if_.eip, &if_.esp);
 
+  sema_up (&args->sema);
+
   /* If load failed, quit. */
-  palloc_free_page (args->file_name);
   if (success) {
     //TODO report success
   } else {
     //TODO report failure
     thread_exit ();
   }
+
   /* Start the user process by simulating a return from an
      interrupt, implemented by intr_exit (in
      threads/intr-stubs.S).  Because intr_exit takes all of its