static void kernel_thread (thread_func *, void *aux);
+static struct thread *running_thread (void);
static struct thread *next_thread_to_run (void);
static struct thread *new_thread (const char *name);
-static bool is_thread (struct thread *t);
-static void *alloc_frame (struct thread *t, size_t size);
-static void destroy_thread (struct thread *t);
+static void init_thread (struct thread *, const char *name);
+static bool is_thread (struct thread *);
+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);
-/* Initializes the threading system. After calling, create some
- threads with thread_create() or thread_execute(), then start
- the scheduler with thread_start(). */
+/* 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.
+
+ After calling this function, be sure to initialize the page
+ allocator before trying to create any threads with
+ thread_create(). */
void
thread_init (void)
{
+ struct thread *t;
+
ASSERT (intr_get_level () == INTR_OFF);
+ /* Set up a thread structure for the running thread. */
+ t = running_thread ();
+ init_thread (t, "main");
+ t->status = THREAD_RUNNING;
+
/* Initialize run queue. */
list_init (&run_queue);
-
- /* Create idle thread. */
- idle_thread = thread_create ("idle", idle, NULL);
- idle_thread->status = THREAD_BLOCKED;
}
-/* Starts the thread scheduler. The caller should have created
- some threads with thread_create() or thread_execute(). Never
- returns to the caller. */
+/* Starts preemptive thread scheduling by enabling interrupts.
+ Also creates the idle thread. */
void
thread_start (void)
{
- struct thread *t = next_thread_to_run ();
- if (t->status == THREAD_READY)
- list_remove (&t->rq_elem);
- t->status = THREAD_RUNNING;
- switch_threads (NULL, t);
+ /* Create idle thread. */
+ idle_thread = thread_create ("idle", idle, NULL);
+ idle_thread->status = THREAD_BLOCKED;
- NOT_REACHED ();
+ /* Enable interrupts. */
+ intr_enable ();
}
/* Creates a new kernel thread named NAME, which executes
return t->name;
}
-/* Returns the running thread. */
+/* Returns the running thread.
+ This is running_thread() plus a couple of sanity checks. */
struct thread *
thread_current (void)
{
- uint32_t *esp;
- struct thread *t;
-
- /* Copy the CPU's stack pointer into `esp', and then round that
- 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));
- t = pg_round_down (esp);
-
+ struct thread *t = running_thread ();
+
/* Make sure T is really a thread.
- If this assertion fires, then your thread may have
- overflowed its stack. Each thread has less than 4 kB of
- stack, so a few big automatic arrays or moderate recursion
- can cause stack overflow. */
+ If either of these assertions fire, then your thread may
+ have overflowed its stack. Each thread has less than 4 kB
+ of stack, so a few big automatic arrays or moderate
+ recursion can cause stack overflow. */
ASSERT (is_thread (t));
+ ASSERT (t->status == THREAD_RUNNING);
return t;
}
thread_exit (); /* If function() returns, kill the thread. */
}
\f
+/* Returns the running thread. */
+struct thread *
+running_thread (void)
+{
+ uint32_t *esp;
+
+ /* Copy the CPU's stack pointer into `esp', and then round that
+ 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));
+ return pg_round_down (esp);
+}
+
/* Returns true if T appears to point to a valid thread. */
static bool
is_thread (struct thread *t)
t = palloc_get (PAL_ZERO);
if (t != NULL)
- {
- strlcpy (t->name, name, sizeof t->name);
- t->stack = (uint8_t *) t + PGSIZE;
- t->status = THREAD_BLOCKED;
- t->magic = THREAD_MAGIC;
- }
-
+ init_thread (t, name);
+
return t;
}
+/* Initializes T as a new thread named NAME. */
+static void
+init_thread (struct thread *t, const char *name)
+{
+ memset (t, 0, sizeof *t);
+ strlcpy (t->name, name, sizeof t->name);
+ t->stack = (uint8_t *) t + PGSIZE;
+ t->status = THREAD_BLOCKED;
+ t->magic = THREAD_MAGIC;
+}
+
/* Allocates a SIZE-byte frame at the top of thread T's stack and
returns a pointer to the frame's base. */
static void *
void
schedule_tail (struct thread *prev)
{
- struct thread *cur = thread_current ();
+ struct thread *cur = running_thread ();
ASSERT (intr_get_level () == INTR_OFF);
static void
schedule (void)
{
- struct thread *cur = thread_current ();
+ struct thread *cur = running_thread ();
struct thread *next = next_thread_to_run ();
+ struct thread *prev = NULL;
ASSERT (intr_get_level () == INTR_OFF);
ASSERT (cur->status != THREAD_RUNNING);
ASSERT (is_thread (next));
if (cur != next)
- {
- struct thread *prev = switch_threads (cur, next);
- schedule_tail (prev);
- }
+ prev = switch_threads (cur, next);
+ schedule_tail (prev);
}
\f
/* Offset of `stack' member within `struct thread'.
projects / pintos-anon / blobdiff