X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=blobdiff_plain;f=src%2Fthreads%2Fthread.c;h=d68c123fb2476420d09557f4f52d4a6fb12949f4;hp=fc358de69a4fe6a3cab2dff5dc594d43515d242c;hb=09fa5c11aff62bd728d4fe8de28a7abaf252fed3;hpb=e49318880e6420e9b5a4ae9ffb986b49f89798e0

diff --git a/src/threads/thread.c b/src/threads/thread.c
index fc358de..d68c123 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -7,13 +7,12 @@
 #include "threads/flags.h"
 #include "threads/interrupt.h"
 #include "threads/intr-stubs.h"
-#include "threads/mmu.h"
 #include "threads/palloc.h"
 #include "threads/switch.h"
 #include "threads/synch.h"
+#include "threads/vaddr.h"
 #ifdef USERPROG
-#include "userprog/addrspace.h"
-#include "userprog/gdt.h"
+#include "userprog/process.h"
 #endif
 
 /* Random value for struct thread's `magic' member.
@@ -25,6 +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;
 
@@ -42,44 +45,59 @@ struct kernel_thread_frame
     void *aux;                  /* Auxiliary data for function. */
   };
 
+/* Statistics. */
+static long long idle_ticks;    /* # of timer ticks spent idle. */
+static long long kernel_ticks;  /* # of timer ticks in kernel threads. */
+static long long user_ticks;    /* # of timer ticks in user programs. */
+
+/* Scheduling. */
+#define TIME_SLICE 4            /* # of timer ticks to give each thread. */
+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 option "-o mlfqs". */
+bool thread_mlfqs;
+
 static void kernel_thread (thread_func *, void *aux);
 
 static void idle (void *aux UNUSED);
 static struct thread *running_thread (void);
 static struct thread *next_thread_to_run (void);
-static struct thread *new_thread (const char *name, int priority);
 static void init_thread (struct thread *, const char *name, int priority);
-static bool is_thread (struct thread *);
+static bool is_thread (struct thread *) UNUSED;
 static void *alloc_frame (struct thread *, size_t size);
-static void destroy_thread (struct thread *);
 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
-   that's currently running into a thread.  Note that this is
-   possible only because the loader was careful to put the bottom
-   of the stack at a page boundary; it won't work in general.
-   Also initializes the run queue.
+   that's currently running into a thread.  This can't work in
+   general and it is possible in this case only because loader.S
+   was careful to put the bottom of the stack at a page boundary.
+
+   Also initializes the run queue and the tid lock.
 
    After calling this function, be sure to initialize the page
    allocator before trying to create any threads with
-   thread_create(). */
+   thread_create().
+
+   It is not safe to call thread_current() until this function
+   finishes. */
 void
 thread_init (void) 
 {
   ASSERT (intr_get_level () == INTR_OFF);
 
-  lock_init (&tid_lock, "tid");
+  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 ();
   init_thread (initial_thread, "main", PRI_DEFAULT);
   initial_thread->status = THREAD_RUNNING;
   initial_thread->tid = allocate_tid ();
-
-  /* Initialize run queue. */
-  list_init (&ready_list);
 }
 
 /* Starts preemptive thread scheduling by enabling interrupts.
@@ -87,19 +105,59 @@ thread_init (void)
 void
 thread_start (void) 
 {
-  thread_create ("idle", PRI_DEFAULT, idle, NULL);
+  /* Create the idle thread. */
+  struct semaphore idle_started;
+  sema_init (&idle_started, 0);
+  thread_create ("idle", PRI_MIN, idle, &idle_started);
+
+  /* Start preemptive thread scheduling. */
   intr_enable ();
+
+  /* Wait for the idle thread to initialize idle_thread. */
+  sema_down (&idle_started);
+}
+
+/* Called by the timer interrupt handler at each timer tick.
+   Thus, this function runs in an external interrupt context. */
+void
+thread_tick (void) 
+{
+  struct thread *t = thread_current ();
+
+  /* Update statistics. */
+  if (t == idle_thread)
+    idle_ticks++;
+#ifdef USERPROG
+  else if (t->pagedir != NULL)
+    user_ticks++;
+#endif
+  else
+    kernel_ticks++;
+
+  /* Enforce preemption. */
+  if (++thread_ticks >= TIME_SLICE)
+    intr_yield_on_return ();
+}
+
+/* Prints thread statistics. */
+void
+thread_print_stats (void) 
+{
+  printf ("Thread: %lld idle ticks, %lld kernel ticks, %lld user ticks\n",
+          idle_ticks, kernel_ticks, user_ticks);
 }
 
 /* Creates a new kernel thread named NAME with the given initial
    PRIORITY, which executes FUNCTION passing AUX as the argument,
-   and adds it to the ready queue.  If thread_start() has been
-   called, then the new thread may be scheduled before
-   thread_create() returns.  It could even exit before
-   thread_create() returns.  Use a semaphore or some other form
-   of synchronization if you need to ensure ordering.  Returns
-   the thread identifier for the new thread, or TID_ERROR if
-   creation fails.
+   and adds it to the ready queue.  Returns the thread identifier
+   for the new thread, or TID_ERROR if creation fails.
+
+   If thread_start() has been called, then the new thread may be
+   scheduled before thread_create() returns.  It could even exit
+   before thread_create() returns.  Contrariwise, the original
+   thread may run for any amount of time before the new thread is
+   scheduled.  Use a semaphore or some other form of
+   synchronization if you need to ensure ordering.
 
    The code provided sets the new thread's `priority' member to
    PRIORITY, but no actual priority scheduling is implemented.
@@ -113,13 +171,23 @@ 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);
 
-  t = new_thread (name, priority);
+  /* Allocate thread. */
+  t = palloc_get_page (PAL_ZERO);
   if (t == NULL)
     return TID_ERROR;
-  tid = t->tid;
+
+  /* Initialize thread. */
+  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);
@@ -134,6 +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);
@@ -141,9 +212,30 @@ thread_create (const char *name, int priority,
   return tid;
 }
 
-/* Transitions a blocked thread T from its current state to the
-   ready-to-run state.  This is an error if T is not blocked.
-   (Use thread_yield() to make the running thread ready.) */
+/* Puts the current thread to sleep.  It will not be scheduled
+   again until awoken by thread_unblock().
+
+   This function must be called with interrupts turned off.  It
+   is usually a better idea to use one of the synchronization
+   primitives in synch.h. */
+void
+thread_block (void) 
+{
+  ASSERT (!intr_context ());
+  ASSERT (intr_get_level () == INTR_OFF);
+
+  thread_current ()->status = THREAD_BLOCKED;
+  schedule ();
+}
+
+/* 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.)
+
+   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) 
 {
@@ -198,9 +290,15 @@ thread_exit (void)
 {
   ASSERT (!intr_context ());
 
-  /* Just set our status to dying and schedule another process.
-     We will be destroyed during the call to schedule_tail(). */
+#ifdef USERPROG
+  process_exit ();
+#endif
+
+  /* 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 ();
@@ -217,43 +315,110 @@ thread_yield (void)
   ASSERT (!intr_context ());
 
   old_level = intr_disable ();
-  list_push_back (&ready_list, &cur->elem);
+  if (cur != idle_thread) 
+    list_push_back (&ready_list, &cur->elem);
   cur->status = THREAD_READY;
   schedule ();
   intr_set_level (old_level);
 }
 
-/* Puts the current thread to sleep.  It will not be scheduled
-   again until awoken by thread_unblock().
-
-   This function must be called with interrupts turned off.  It
-   is usually a better idea to use one of the synchronization
-   primitives in synch.h. */
+/* Invoke function 'func' on all threads, passing along 'aux'.
+   This function must be called with interrupts off. */
 void
-thread_block (void) 
+thread_foreach (thread_action_func *func, void *aux)
 {
-  ASSERT (!intr_context ());
+  struct list_elem *e;
+
   ASSERT (intr_get_level () == INTR_OFF);
 
-  thread_current ()->status = THREAD_BLOCKED;
-  schedule ();
+  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) 
+{
+  thread_current ()->priority = new_priority;
+}
+
+/* Returns the current thread's priority. */
+int
+thread_get_priority (void) 
+{
+  return thread_current ()->priority;
+}
+
+/* Sets the current thread's nice value to NICE. */
+void
+thread_set_nice (int nice UNUSED) 
+{
+  /* Not yet implemented. */
+}
+
+/* Returns the current thread's nice value. */
+int
+thread_get_nice (void) 
+{
+  /* Not yet implemented. */
+  return 0;
+}
+
+/* Returns 100 times the system load average. */
+int
+thread_get_load_avg (void) 
+{
+  /* Not yet implemented. */
+  return 0;
+}
+
+/* Returns 100 times the current thread's recent_cpu value. */
+int
+thread_get_recent_cpu (void) 
+{
+  /* Not yet implemented. */
+  return 0;
 }
 
-/* Idle thread.  Executes when no other thread is ready to run. */
+/* Idle thread.  Executes when no other thread is ready to run.
+
+   The idle thread is initially put on the ready list by
+   thread_start().  It will be scheduled once initially, at which
+   point it initializes idle_thread, "up"s the semaphore passed
+   to it to enable thread_start() to continue, and immediately
+   blocks.  After that, the idle thread never appears in the
+   ready list.  It is returned by next_thread_to_run() as a
+   special case when the ready list is empty. */
 static void
-idle (void *aux UNUSED) 
+idle (void *idle_started_ UNUSED) 
 {
+  struct semaphore *idle_started = idle_started_;
   idle_thread = thread_current ();
+  sema_up (idle_started);
 
   for (;;) 
     {
       /* Let someone else run. */
       intr_disable ();
       thread_block ();
-      intr_enable ();
 
-      /* Use CPU `hlt' instruction to wait for interrupt. */
-      asm ("hlt");
+      /* Re-enable interrupts and wait for the next one.
+
+         The `sti' instruction disables interrupts until the
+         completion of the next instruction, so these two
+         instructions are executed atomically.  This atomicity is
+         important; otherwise, an interrupt could be handled
+         between re-enabling interrupts and waiting for the next
+         one to occur, wasting as much as one clock tick worth of
+         time.
+
+         See [IA32-v2a] "HLT", [IA32-v2b] "STI", and [IA32-v3a]
+         7.11.1 "HLT Instruction". */
+      asm volatile ("sti; hlt" : : : "memory");
     }
 }
 
@@ -278,38 +443,24 @@ running_thread (void)
      down to the start of a page.  Because `struct thread' is
      always at the beginning of a page and the stack pointer is
      somewhere in the middle, this locates the curent thread. */
-  asm ("movl %%esp, %0\n" : "=g" (esp));
+  asm ("mov %%esp, %0" : "=g" (esp));
   return pg_round_down (esp);
 }
 
 /* Returns true if T appears to point to a valid thread. */
 static bool
-is_thread (struct thread *t) 
+is_thread (struct thread *t)
 {
   return t != NULL && t->magic == THREAD_MAGIC;
 }
 
-/* Creates a new thread named NAME as a child of the running
-   thread.  Returns the new thread if successful or a null
-   pointer on failure. */
-static struct thread *
-new_thread (const char *name, int priority)
-{
-  struct thread *t = palloc_get (PAL_ZERO);
-  if (t != NULL) 
-    {
-      init_thread (t, name, priority);
-      t->tid = allocate_tid ();
-    }
-
-  return t;
-}
-
 /* Does basic initialization of T as a blocked thread named
    NAME. */
 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);
@@ -320,6 +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
@@ -349,20 +504,6 @@ next_thread_to_run (void)
     return list_entry (list_pop_front (&ready_list), struct thread, elem);
 }
 
-/* Destroys T, which must not be the running thread. */
-static void
-destroy_thread (struct thread *t) 
-{
-  ASSERT (is_thread (t));
-  ASSERT (t != thread_current ());
-
-#ifdef USERPROG
-  addrspace_destroy (t);
-#endif
-  if (t != initial_thread)
-    palloc_free (t);
-}
-
 /* Completes a thread switch by activating the new thread's page
    tables, and, if the previous thread is dying, destroying it.
 
@@ -373,10 +514,14 @@ destroy_thread (struct thread *t)
    the first time a thread is scheduled it is called by
    switch_entry() (see switch.S).
 
+   It's not safe to call printf() until the thread switch is
+   complete.  In practice that means that printf()s should be
+   added at the end of the function.
+
    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 ();
   
@@ -385,22 +530,33 @@ schedule_tail (struct thread *prev)
   /* Mark us as running. */
   cur->status = THREAD_RUNNING;
 
+  /* Start new time slice. */
+  thread_ticks = 0;
+
 #ifdef USERPROG
   /* Activate the new address space. */
-  addrspace_activate ();
+  process_activate ();
 #endif
 
-  /* If the thread we switched from is dying, destroy it.
-     This must happen late because it's not a good idea to
-     e.g. destroy the page table you're currently using. */
-  if (prev != NULL && prev->status == THREAD_DYING) 
-    destroy_thread (prev);
+  /* If the thread we switched from is dying, destroy its struct
+     thread.  This must happen late so that thread_exit() doesn't
+     pull out the rug under itself.  (We don't free
+     initial_thread because its memory was not obtained via
+     palloc().) */
+  if (prev != NULL && prev->status == THREAD_DYING && prev != initial_thread) 
+    {
+      ASSERT (prev != cur);
+      palloc_free_page (prev);
+    }
 }
 
 /* Schedules a new process.  At entry, interrupts must be off and
    the running process's state must have been changed from
    running to some other state.  This function finds another
-   thread to run and switches to it. */
+   thread to run and switches to it.
+
+   It's not safe to call printf() until thread_schedule_tail()
+   has completed. */
 static void
 schedule (void) 
 {
@@ -414,7 +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. */