implement wait

3 files changed, 42 insertions, 14 deletions

diff --git a/src/threads/thread.h b/src/threads/thread.h
index fdaba60..4b33d7d 100644
--- a/src/threads/thread.h
+++ b/src/threads/thread.h
@@ -30,10 +30,10 @@ struct parent_child
   {
     struct list_elem elem; // owned by the parent
 
-    // struct semaphore exit_sema;
+    struct semaphore exit_sema;
+    int exit_status;
 
     struct lock l;
-    int exit_status;
     int alive_count;
     tid_t child_tid;
   };
@@ -116,6 +116,7 @@ struct thread
     /* Owned by userprog/process.c. */
     uint32_t *pagedir;                  /* Page directory. */
     struct file **fds;                  /* Pointer to array of file descriptors. */
+    bool load_success;
 
     struct parent_child *parent; // one parent
     struct list children; // multiple children
diff --git a/src/userprog/process.c b/src/userprog/process.c
index 589b48b..fadd14d 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -93,11 +93,12 @@ start_process (void *args_)
   if_.eflags = FLAG_IF | FLAG_MBS;
   success = load (args->file_name, &if_.eip, &if_.esp);
   args->success = success;
+  t->load_success = success;
 
   if (success) {
     t->parent = malloc (sizeof (struct parent_child));
 
-    // sema_init (&t->parent.exit_sema, 0);
+    sema_init (&t->parent->exit_sema, 0);
     lock_init (&t->parent->l);
 
     t->parent->child_tid = t->tid;
@@ -132,9 +133,22 @@ start_process (void *args_)
    This function will be implemented in problem 2-2.  For now, it
    does nothing. */
 int
-process_wait (tid_t child_tid UNUSED) 
+process_wait (tid_t child_tid)
 {
-  for (;;) {}
+  struct thread *t = thread_current ();
+  struct list_elem *e;
+  for (e = list_begin (&t->children); e != list_end (&t->children);
+       e = list_next (e))
+  {
+    struct parent_child *pc = list_entry (e, struct parent_child, elem);
+    if (child_tid == pc->child_tid) {
+      sema_down (&pc->exit_sema);
+      int exit_status = pc->exit_status;
+      pc->exit_status = -1;
+      return exit_status;
+    }
+  }
+  return -1;
 }
 
 static void
@@ -157,14 +171,18 @@ process_exit (void)
   struct thread *cur = thread_current ();
   uint32_t *pd;
 
-  free_pc (cur->parent);
+  if (cur->load_success) {
+    sema_up (&cur->parent->exit_sema);
+    free_pc (cur->parent);
+    printf("%s: exit(%d)\n", cur->name, cur->parent->exit_status);
 
-  struct list_elem *e;
-  struct parent_child *child;
-  while (!list_empty (&cur->children)) {
-    e = list_pop_front (&cur->children);
-    child = list_entry (e, struct parent_child, elem);
-    free_pc (child);
+    struct list_elem *e;
+    struct parent_child *child;
+    while (!list_empty (&cur->children)) {
+      e = list_pop_front (&cur->children);
+      child = list_entry (e, struct parent_child, elem);
+      free_pc (child);
+    }
   }
 
   /* Destroy the current process's page directory and switch back
@@ -318,6 +336,7 @@ load (const char *file_name, void (**eip) (void), void **esp)
   }
 
   file_name = esp_cmd;
+  strlcpy (thread_current ()->name, file_name, 16);
 
   /* argv entries are pointers so they need to be aligned to the pointer size. */
   size_t psize = sizeof (char *);
diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 177cf02..52526aa 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -88,12 +88,16 @@ exit (int status)
   thread->parent->exit_status = status;
   lock_release (&thread->parent->l);
 
-  printf("%s: exit(%d)\n", thread->name, status);
-
   thread_exit ();
 }
 
 static int
+wait (tid_t child_tid)
+{
+  return process_wait (child_tid);
+}
+
+static int
 read (int fd_i, void *buf, unsigned size)
 {
   struct thread *thread = thread_current ();
@@ -178,6 +182,10 @@ syscall_handler (struct intr_frame *f UNUSED)
       // exec
       f->eax = exec (INTR_ESP (1, char *));
       break;
+    case 3:
+      // wait
+      f->eax = wait (INTR_ESP (1, tid_t));
+      break;
     case 4:
       // create
       f->eax = create (INTR_ESP (1, char *), INTR_ESP (2, off_t));