From: Ben Pfaff <blp@cs.stanford.edu>
Date: Thu, 16 Sep 2004 21:07:03 +0000 (+0000)
Subject: Invent tid_t data type and use it in many places where we current use
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5fa7a9e2a12522684b0fbaa7d06555544563f124;p=pintos-anon

Invent tid_t data type and use it in many places where we current use
struct thread *.
Remove thread_name() argument.
---

diff --git a/src/threads/synch.c b/src/threads/synch.c
index 169128d..be8f0a5 100644
--- a/src/threads/synch.c
+++ b/src/threads/synch.c
@@ -111,14 +111,13 @@ static void sema_test_helper (void *sema_);
 void
 sema_self_test (void) 
 {
-  struct thread *thread;
   struct semaphore sema[2];
   int i;
 
   printf ("Testing semaphores...");
   sema_init (&sema[0], 0, "ping");
   sema_init (&sema[1], 0, "pong");
-  thread = thread_create ("sema-test", sema_test_helper, &sema);
+  thread_create ("sema-test", sema_test_helper, &sema);
   for (i = 0; i < 10; i++) 
     {
       sema_up (&sema[0]);
diff --git a/src/threads/test.c b/src/threads/test.c
index ccb2427..4c7bfed 100644
--- a/src/threads/test.c
+++ b/src/threads/test.c
@@ -25,7 +25,7 @@ struct sleep_thread_data
     int *product;               /* Largest product so far. */
     struct lock *lock;          /* Lock on access to `product'. */
     struct semaphore done;      /* Completion semaphore. */
-    struct thread *thread;      /* Thread. */
+    tid_t tid;                  /* Thread ID. */
   };
 
 static void sleeper (void *);
@@ -63,14 +63,14 @@ test_sleep (int iterations)
       t->product = &product;
       t->lock = &lock;
       sema_init (&t->done, 0, name);
-      t->thread = thread_create (name, sleeper, t);
+      t->tid = thread_create (name, sleeper, t);
     }
   
   /* Wait for all the threads to finish. */
   for (i = 0; i < thread_cnt; i++) 
     {
 #ifdef THREAD_JOIN_IMPLEMENTED
-      thread_join (threads[i].thread);
+      thread_join (threads[i].tid);
 #else
       sema_down (&threads[i].done);
 #endif
@@ -98,13 +98,11 @@ sleeper (void *t_)
       lock_release (t->lock);
 
       printf ("%s: duration=%d, iteration=%d, product=%d\n",
-              thread_name (thread_current ()),
-              t->duration, i, new_product);
+              thread_name (), t->duration, i, new_product);
 
       if (old_product > new_product)
         printf ("%s: Out of order sleep completion (%d > %d)!\n",
-                thread_name (thread_current ()),
-                old_product, new_product);
+                thread_name (), old_product, new_product);
     }
   
   /* Signal completion. */
diff --git a/src/threads/thread.c b/src/threads/thread.c
index 1b56f98..5400f78 100644
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -8,27 +8,29 @@
 #include "threads/mmu.h"
 #include "threads/palloc.h"
 #include "threads/switch.h"
+#include "threads/synch.h"
 #ifdef USERPROG
 #include "userprog/gdt.h"
 #endif
 
-/* Value for struct thread's `magic' member.
+/* Random value for struct thread's `magic' member.
    Used to detect stack overflow.  See the big comment at the top
    of thread.h for details. */
-#define THREAD_MAGIC 0x1234abcdu
+#define THREAD_MAGIC 0xcd6abf4b
 
 /* List of processes in THREAD_READY state, that is, processes
    that are ready to run but not actually running. */
 static struct list ready_list;
 
 /* Idle thread. */
-static struct thread *idle_thread;      /* Thread. */
-static void idle (void *aux UNUSED);    /* Thread function. */
+static struct thread *idle_thread;
 
-/* Initial thread.
-   This is the thread running main(). */
+/* Initial thread, the thread running init.c:main(). */
 static struct thread *initial_thread;
 
+/* Lock used by allocate_tid(). */
+static struct lock tid_lock;
+
 /* Stack frame for kernel_thread(). */
 struct kernel_thread_frame 
   {
@@ -39,6 +41,7 @@ struct kernel_thread_frame
 
 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);
@@ -48,6 +51,7 @@ 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);
+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
@@ -63,10 +67,13 @@ thread_init (void)
 {
   ASSERT (intr_get_level () == INTR_OFF);
 
+  lock_init (&tid_lock, "tid");
+
   /* Set up a thread structure for the running thread. */
   initial_thread = running_thread ();
   init_thread (initial_thread, "main");
   initial_thread->status = THREAD_RUNNING;
+  initial_thread->tid = allocate_tid ();
 
   /* Initialize run queue. */
   list_init (&ready_list);
@@ -77,31 +84,33 @@ thread_init (void)
 void
 thread_start (void) 
 {
-  /* Create idle thread. */
-  idle_thread = thread_create ("idle", idle, NULL);
-  idle_thread->status = THREAD_BLOCKED;
-
-  /* Enable interrupts. */
+  thread_create ("idle", idle, NULL);
   intr_enable ();
 }
 
 /* Creates a new kernel thread named NAME, 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.  Use a
-   semaphore or some other form of synchronization if you need to
-   ensure ordering. */
-struct 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. */
+tid_t
 thread_create (const char *name, thread_func *function, void *aux) 
 {
   struct thread *t;
   struct kernel_thread_frame *kf;
   struct switch_entry_frame *ef;
   struct switch_threads_frame *sf;
+  tid_t tid;
 
   ASSERT (function != NULL);
 
   t = new_thread (name);
+  if (t == NULL)
+    return TID_ERROR;
+  tid = t->tid = allocate_tid ();
 
   /* Stack frame for kernel_thread(). */
   kf = alloc_frame (t, sizeof *kf);
@@ -120,7 +129,7 @@ thread_create (const char *name, thread_func *function, void *aux)
   /* Add to run queue. */
   thread_unblock (t);
 
-  return t;
+  return tid;
 }
 
 #ifdef USERPROG
@@ -128,7 +137,7 @@ thread_create (const char *name, thread_func *function, void *aux)
    FILENAME, and adds it to the ready queue.  If thread_start()
    has been called, then new thread may be scheduled before
    thread_execute() returns.*/
-bool
+tid_t
 thread_execute (const char *filename) 
 {
   struct thread *t;
@@ -136,12 +145,14 @@ thread_execute (const char *filename)
   struct switch_entry_frame *ef;
   struct switch_threads_frame *sf;
   void (*start) (void);
+  tid_t tid;
 
   ASSERT (filename != NULL);
 
   t = new_thread (filename);
   if (t == NULL)
-    return false;
+    return TID_ERROR;
+  tid = t->tid = allocate_tid ();
   
   if (!addrspace_load (t, filename, &start)) 
     PANIC ("%s: program load failed", filename);
@@ -167,7 +178,7 @@ thread_execute (const char *filename)
   /* Add to run queue. */
   thread_unblock (t);
 
-  return true;
+  return tid;
 }
 #endif
 
@@ -190,12 +201,11 @@ thread_unblock (struct thread *t)
   intr_set_level (old_level);
 }
 
-/* Returns the name of thread T. */
+/* Returns the name of the running thread. */
 const char *
-thread_name (struct thread *t) 
+thread_name (void) 
 {
-  ASSERT (is_thread (t));
-  return t->name;
+  return thread_current ()->name;
 }
 
 /* Returns the running thread.
@@ -217,6 +227,13 @@ thread_current (void)
   return t;
 }
 
+/* Returns the running thread's tid. */
+tid_t
+thread_tid (void) 
+{
+  return thread_current ()->tid;
+}
+
 /* Deschedules the current thread and destroys it.  Never
    returns to the caller. */
 void
@@ -269,16 +286,17 @@ thread_block (void)
 static void
 idle (void *aux UNUSED) 
 {
+  idle_thread = thread_current ();
+
   for (;;) 
     {
-      /* Wait for an interrupt. */
-      DEBUG (idle, "idle");
-      asm ("hlt");
-
       /* Let someone else run. */
       intr_disable ();
       thread_block ();
       intr_enable ();
+
+      /* Use CPU `hlt' instruction to wait for interrupt. */
+      asm ("hlt");
     }
 }
 
@@ -336,9 +354,9 @@ static void
 init_thread (struct thread *t, const char *name)
 {
   memset (t, 0, sizeof *t);
+  t->status = THREAD_BLOCKED;
   strlcpy (t->name, name, sizeof t->name);
   t->stack = (uint8_t *) t + PGSIZE;
-  t->status = THREAD_BLOCKED;
   t->magic = THREAD_MAGIC;
 }
 
@@ -438,6 +456,20 @@ schedule (void)
     prev = switch_threads (cur, next);
   schedule_tail (prev); 
 }
+
+/* Returns a tid to use for a new thread. */
+static tid_t
+allocate_tid (void) 
+{
+  static tid_t next_tid = 1;
+  tid_t tid;
+
+  lock_acquire (&tid_lock);
+  tid = next_tid++;
+  lock_release (&tid_lock);
+
+  return tid;
+}
 
 /* Offset of `stack' member within `struct thread'.
    Used by switch.S, which can't figure it out on its own. */
diff --git a/src/threads/thread.h b/src/threads/thread.h
index 248f1d4..e844b5c 100644
--- a/src/threads/thread.h
+++ b/src/threads/thread.h
@@ -18,6 +18,11 @@ enum thread_status
     THREAD_DYING        /* About to be destroyed. */
   };
 
+/* Thread identifier type.
+   You can redefine this to whatever type you like. */
+typedef int tid_t;
+#define TID_ERROR ((tid_t) -1)          /* Error value for tid_t. */
+
 /* A kernel thread or user process.
 
    Each thread structure is stored in its own 4 kB page.  The
@@ -76,14 +81,17 @@ enum thread_status
    blocked state is on a semaphore wait list. */
 struct thread
   {
-    /* These members are owned by the thread_*() functions. */
+    /* These members are owned by thread.c. */
+    tid_t tid;                          /* Thread identifier. */
     enum thread_status status;          /* Thread state. */
     char name[16];                      /* Name (for debugging purposes). */
     uint8_t *stack;                     /* Saved stack pointer. */
+
+    /* Shared between thread.c and synch.c. */
     list_elem elem;                     /* List element. */
 
 #ifdef USERPROG
-    /* These members are owned by the addrspace_*() functions. */
+    /* These members are owned by userprog/addrspace.c. */
     uint32_t *pagedir;                  /* Page directory. */
 #endif
 
@@ -95,21 +103,23 @@ void thread_init (void);
 void thread_start (void);
 
 typedef void thread_func (void *aux);
-struct thread *thread_create (const char *name, thread_func *, void *);
+tid_t thread_create (const char *name, thread_func *, void *);
 #ifdef USERPROG
-bool thread_execute (const char *filename);
+tid_t thread_execute (const char *filename);
 #endif
 
 void thread_unblock (struct thread *);
-const char *thread_name (struct thread *);
 
 struct thread *thread_current (void);
+tid_t thread_tid (void);
+const char *thread_name (void);
 void thread_exit (void) NO_RETURN;
 void thread_yield (void);
 void thread_block (void);
 
-void thread_join (struct thread *);
-void thread_set_priority (struct thread *, int);
-int thread_get_priority (const struct thread *);
+/* These functions will be implemented in project 1. */
+void thread_join (tid_t);
+void thread_set_priority (tid_t, int);
+int thread_get_priority (tid_t);
 
 #endif /* threads/thread.h */
diff --git a/src/userprog/exception.c b/src/userprog/exception.c
index 4e9d28f..dead766 100644
--- a/src/userprog/exception.c
+++ b/src/userprog/exception.c
@@ -74,8 +74,7 @@ kill (struct intr_frame *f)
       /* User's code segment, so it's a user exception, as we
          expected.  Kill the user process.  */
       printf ("%s: dying due to interrupt %#04x (%s).\n",
-              thread_name (thread_current ()),
-              f->vec_no, intr_name (f->vec_no));
+              thread_name (), f->vec_no, intr_name (f->vec_no));
       intr_dump_frame (f);
       thread_exit ();