thread: Properly protect 'all_list' around insertion.

[pintos-anon] / src / threads / thread.c

diff --git a/src/threads/thread.c b/src/threads/thread.c
index 938d7f87d6b0b296e676ca971928a6ba0823fd27..d68c123fb2476420d09557f4f52d4a6fb12949f4 100644 (file)
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -24,6 +24,10 @@
    that are ready to run but not actually running. */
 static struct list ready_list;
 
+/* List of all processes.  Processes are added to this list
+   when they are first scheduled and removed when they exit. */
+static struct list all_list;
+
 /* Idle thread. */
 static struct thread *idle_thread;
 
@@ -52,9 +56,7 @@ static unsigned thread_ticks;   /* # of timer ticks since last yield. */
 
 /* If false (default), use round-robin scheduler.
    If true, use multi-level feedback queue scheduler.
-   Controlled by kernel command-line options "-o mlfqs".
-   Note that the command line is not parsed until well after
-   thread_init() is called. */
+   Controlled by kernel command-line option "-o mlfqs". */
 bool thread_mlfqs;
 
 static void kernel_thread (thread_func *, void *aux);
@@ -66,7 +68,7 @@ static void init_thread (struct thread *, const char *name, int priority);
 static bool is_thread (struct thread *) UNUSED;
 static void *alloc_frame (struct thread *, size_t size);
 static void schedule (void);
-void schedule_tail (struct thread *prev);
+void thread_schedule_tail (struct thread *prev);
 static tid_t allocate_tid (void);
 
 /* Initializes the threading system by transforming the code
@@ -80,10 +82,6 @@ static tid_t allocate_tid (void);
    allocator before trying to create any threads with
    thread_create().
 
-   The kernel command line is not parsed until *after* this
-   function returns, so that when this function runs,
-   thread_mlfqs is always false.
-
    It is not safe to call thread_current() until this function
    finishes. */
 void
@@ -93,6 +91,7 @@ thread_init (void)
 
   lock_init (&tid_lock);
   list_init (&ready_list);
+  list_init (&all_list);
 
   /* Set up a thread structure for the running thread. */
   initial_thread = running_thread ();
@@ -102,10 +101,7 @@ thread_init (void)
 }
 
 /* Starts preemptive thread scheduling by enabling interrupts.
-   Also creates the idle thread.
-
-   By the time this function runs, thread_mlfqs has been properly
-   initialized to its final value. */
+   Also creates the idle thread. */
 void
 thread_start (void) 
 {
@@ -175,6 +171,7 @@ thread_create (const char *name, int priority,
   struct switch_entry_frame *ef;
   struct switch_threads_frame *sf;
   tid_t tid;
+  enum intr_level old_level;
 
   ASSERT (function != NULL);
 
@@ -187,6 +184,11 @@ thread_create (const char *name, int priority,
   init_thread (t, name, priority);
   tid = t->tid = allocate_tid ();
 
+  /* Prepare thread for first run by initializing its stack.
+     Do this atomically so intermediate values for the 'stack' 
+     member cannot be observed. */
+  old_level = intr_disable ();
+
   /* Stack frame for kernel_thread(). */
   kf = alloc_frame (t, sizeof *kf);
   kf->eip = NULL;
@@ -200,6 +202,9 @@ thread_create (const char *name, int priority,
   /* Stack frame for switch_threads(). */
   sf = alloc_frame (t, sizeof *sf);
   sf->eip = switch_entry;
+  sf->ebp = 0;
+
+  intr_set_level (old_level);
 
   /* Add to run queue. */
   thread_unblock (t);
@@ -225,7 +230,12 @@ thread_block (void)
 
 /* Transitions a blocked thread T to the ready-to-run state.
    This is an error if T is not blocked.  (Use thread_yield() to
-   make the running thread ready.) */
+   make the running thread ready.)
+
+   This function does not preempt the running thread.  This can
+   be important: if the caller had disabled interrupts itself,
+   it may expect that it can atomically unblock a thread and
+   update other data. */
 void
 thread_unblock (struct thread *t) 
 {
@@ -284,9 +294,11 @@ thread_exit (void)
   process_exit ();
 #endif
 
-  /* Just set our status to dying and schedule another process.
-     We will be destroyed during the call to schedule_tail(). */
+  /* Remove thread from all threads list, set our status to dying,
+     and schedule another process.  That process will destroy us
+     when it calls thread_schedule_tail(). */
   intr_disable ();
+  list_remove (&thread_current()->allelem);
   thread_current ()->status = THREAD_DYING;
   schedule ();
   NOT_REACHED ();
@@ -310,6 +322,23 @@ thread_yield (void)
   intr_set_level (old_level);
 }
 
+/* Invoke function 'func' on all threads, passing along 'aux'.
+   This function must be called with interrupts off. */
+void
+thread_foreach (thread_action_func *func, void *aux)
+{
+  struct list_elem *e;
+
+  ASSERT (intr_get_level () == INTR_OFF);
+
+  for (e = list_begin (&all_list); e != list_end (&all_list);
+       e = list_next (e))
+    {
+      struct thread *t = list_entry (e, struct thread, allelem);
+      func (t, aux);
+    }
+}
+
 /* Sets the current thread's priority to NEW_PRIORITY. */
 void
 thread_set_priority (int new_priority) 
@@ -389,7 +418,7 @@ idle (void *idle_started_ UNUSED)
 
          See [IA32-v2a] "HLT", [IA32-v2b] "STI", and [IA32-v3a]
          7.11.1 "HLT Instruction". */
-      asm ("sti; hlt");
+      asm volatile ("sti; hlt" : : : "memory");
     }
 }
 
@@ -430,6 +459,8 @@ is_thread (struct thread *t)
 static void
 init_thread (struct thread *t, const char *name, int priority)
 {
+  enum intr_level old_level;
+
   ASSERT (t != NULL);
   ASSERT (PRI_MIN <= priority && priority <= PRI_MAX);
   ASSERT (name != NULL);
@@ -440,6 +471,10 @@ init_thread (struct thread *t, const char *name, int priority)
   t->stack = (uint8_t *) t + PGSIZE;
   t->priority = priority;
   t->magic = THREAD_MAGIC;
+
+  old_level = intr_disable ();
+  list_push_back (&all_list, &t->allelem);
+  intr_set_level (old_level);
 }
 
 /* Allocates a SIZE-byte frame at the top of thread T's stack and
@@ -486,7 +521,7 @@ next_thread_to_run (void)
    After this function and its caller returns, the thread switch
    is complete. */
 void
-schedule_tail (struct thread *prev) 
+thread_schedule_tail (struct thread *prev)
 {
   struct thread *cur = running_thread ();
   
@@ -520,8 +555,8 @@ schedule_tail (struct thread *prev)
    running to some other state.  This function finds another
    thread to run and switches to it.
 
-   It's not safe to call printf() until schedule_tail() has
-   completed. */
+   It's not safe to call printf() until thread_schedule_tail()
+   has completed. */
 static void
 schedule (void) 
 {
@@ -535,7 +570,7 @@ schedule (void)
 
   if (cur != next)
     prev = switch_threads (cur, next);
-  schedule_tail (prev); 
+  thread_schedule_tail (prev);
 }
 
 /* Returns a tid to use for a new thread. */