Add child and own process result information to struct thread

src/threads/thread.h

@@ -4,6 +4,8 @@
 #include <debug.h>
 #include <list.h>
 #include <stdint.h>
+#include <stdbool.h>
+#include "threads/synch.h"
 #include "threads/fixed-point.h"
 
 /* States in a thread's life cycle. */
@@ -29,6 +31,19 @@ typedef int tid_t;
 #define NICE_DEFAULT 0 /* Default niceness. */
 #define NICE_MAX 20    /* Highest niceness. */
 
+/* A process result, synchronised between parent and child. */
+struct process_result
+{
+  tid_t tid;        /* The tid of the child process. */
+  int exit_status;  /* The exit status of the child process. Initially set to
+                       -1, then to 0 when parent dies, or to exit_status when
+                       child dies (whichever happens first). */
+  struct lock lock; /* Lock to synchronise access to the exit_status. */
+  struct semaphore sema; /* Semaphore to signal the parent that the exit_status
+                            has been set. */
+  struct list_elem elem; /* List element for the parent's children list. */
+};
+
 /* A kernel thread or user process.
 
    Each thread structure is stored in its own 4 kB page.  The
@@ -108,6 +123,11 @@ struct thread
     int nice;                           /* Nice value for this thread */
     fp32_t recent_cpu;                  /* Amount of time this process received */
 
+    /* Process wait properties. */
+    struct process_result *result;      /* Result of the process. */
+    struct list child_results;          /* List of children's of this thread
+                                           process results. */
+
     /* Shared between thread.c and synch.c. */
     struct list_elem elem;              /* List element. */