-#include "thread.h"
+#include "threads/thread.h"
+#include <debug.h>
#include <stddef.h>
-#include "debug.h"
-#include "interrupt.h"
-#include "intr-stubs.h"
-#include "lib.h"
-#include "mmu.h"
-#include "palloc.h"
-#include "random.h"
-#include "switch.h"
+#include <random.h>
+#include <stdio.h>
+#include <string.h>
+#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"
#ifdef USERPROG
-#include "gdt.h"
+#include "userprog/process.h"
#endif
-#define THREAD_MAGIC 0x1234abcdu
+/* 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 0xcd6abf4b
/* List of processes in THREAD_READY state, that is, processes
that are ready to run but not actually running. */
-static struct list run_queue;
+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, 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
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. */
+
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);
-static void init_thread (struct thread *, const char *name);
+static void init_thread (struct thread *, const char *name, int priority);
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);
+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
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;
+ lock_init (&tid_lock, "tid");
+ list_init (&ready_list);
- /* Initialize run queue. */
- list_init (&run_queue);
+ /* 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 ();
}
/* Starts preemptive thread scheduling by enabling interrupts.
void
thread_start (void)
{
- /* Create idle thread. */
- idle_thread = thread_create ("idle", idle, NULL);
- idle_thread->status = THREAD_BLOCKED;
-
- /* Enable interrupts. */
+ thread_create ("idle", PRI_DEFAULT, 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 *
-thread_create (const char *name, thread_func *function, void *aux)
+/* Called by the timer interrupt handler at each timer tick to
+ update statistics. */
+void
+thread_tick (void)
+{
+ struct thread *t = thread_current ();
+ if (t == idle_thread)
+ idle_ticks++;
+#ifdef USERPROG
+ else if (t->pagedir != NULL)
+ user_ticks++;
+#endif
+ else
+ kernel_ticks++;
+}
+
+/* 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.
+
+ The code provided sets the new thread's `priority' member to
+ PRIORITY, but no actual priority scheduling is implemented.
+ Priority scheduling is the goal of Problem 1-3. */
+tid_t
+thread_create (const char *name, int priority,
+ 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);
+ /* Allocate thread. */
+ t = palloc_get_page (PAL_ZERO);
+ if (t == NULL)
+ return TID_ERROR;
+
+ /* Initialize thread. */
+ init_thread (t, name, priority);
+ tid = t->tid = allocate_tid ();
/* Stack frame for kernel_thread(). */
kf = alloc_frame (t, sizeof *kf);
/* Add to run queue. */
thread_unblock (t);
- return t;
+ return tid;
}
-#ifdef USERPROG
-/* Starts a new thread running a user program loaded from
- 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
-thread_execute (const char *filename)
-{
- struct thread *t;
- struct intr_frame *if_;
- struct switch_entry_frame *ef;
- struct switch_threads_frame *sf;
- void (*start) (void);
-
- ASSERT (filename != NULL);
-
- t = new_thread (filename);
- if (t == NULL)
- return false;
-
- if (!addrspace_load (t, filename, &start))
- PANIC ("%s: program load failed", filename);
-
- /* Interrupt frame. */
- if_ = alloc_frame (t, sizeof *if_);
- if_->es = SEL_UDSEG;
- if_->ds = SEL_UDSEG;
- if_->eip = start;
- if_->cs = SEL_UCSEG;
- if_->eflags = FLAG_IF | FLAG_MBS;
- if_->esp = PHYS_BASE;
- if_->ss = SEL_UDSEG;
-
- /* Stack frame for switch_entry(). */
- ef = alloc_frame (t, sizeof *ef);
- ef->eip = intr_exit;
-
- /* Stack frame for switch_threads(). */
- sf = alloc_frame (t, sizeof *sf);
- sf->eip = switch_entry;
+/* Puts the current thread to sleep. It will not be scheduled
+ again until awoken by thread_unblock().
- /* Add to run queue. */
- thread_unblock (t);
+ 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);
- return true;
+ thread_current ()->status = THREAD_BLOCKED;
+ schedule ();
}
-#endif
-/* Transitions a blocked thread T from its current state to the
- ready-to-run state. If T is not blocked, there is no effect.
- (Use thread_yield() to make the running thread ready.) */
+/* 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.) */
void
thread_unblock (struct thread *t)
{
ASSERT (is_thread (t));
old_level = intr_disable ();
- if (t->status == THREAD_BLOCKED)
- {
- list_push_back (&run_queue, &t->rq_elem);
- t->status = THREAD_READY;
- }
+ ASSERT (t->status == THREAD_BLOCKED);
+ list_push_back (&ready_list, &t->elem);
+ t->status = THREAD_READY;
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.
- This is running_thread() plus a couple of sanity checks. */
+ This is running_thread() plus a couple of sanity checks.
+ See the big comment at the top of thread.h for details. */
struct thread *
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
{
ASSERT (!intr_context ());
+#ifdef USERPROG
+ process_exit ();
+#endif
+
+ /* Just set our status to dying and schedule another process.
+ We will be destroyed during the call to schedule_tail(). */
intr_disable ();
thread_current ()->status = THREAD_DYING;
schedule ();
ASSERT (!intr_context ());
old_level = intr_disable ();
- list_push_back (&run_queue, &cur->rq_elem);
+ 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(). */
-void
-thread_block (void)
-{
- ASSERT (!intr_context ());
- ASSERT (intr_get_level () == INTR_OFF);
-
- thread_current ()->status = THREAD_BLOCKED;
- schedule ();
-}
\f
/* Idle thread. Executes when no other thread is ready to run. */
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");
}
}
return t != NULL && t->magic == THREAD_MAGIC;
}
-/* Creates a new thread named NAME and initializes its fields.
- Returns the new thread if successful or a null pointer on
- failure. */
-static struct thread *
-new_thread (const char *name)
+/* Does basic initialization of T as a blocked thread named
+ NAME. */
+static void
+init_thread (struct thread *t, const char *name, int priority)
{
- struct thread *t;
-
+ ASSERT (t != NULL);
+ ASSERT (PRI_MIN <= priority && priority <= PRI_MAX);
ASSERT (name != NULL);
-
- t = palloc_get (PAL_ZERO);
- if (t != NULL)
- 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);
+ t->status = THREAD_BLOCKED;
strlcpy (t->name, name, sizeof t->name);
t->stack = (uint8_t *) t + PGSIZE;
- t->status = THREAD_BLOCKED;
+ t->priority = priority;
t->magic = THREAD_MAGIC;
}
static struct thread *
next_thread_to_run (void)
{
- if (list_empty (&run_queue))
+ if (list_empty (&ready_list))
return idle_thread;
else
- return list_entry (list_pop_front (&run_queue), struct thread, rq_elem);
-}
-
-/* Destroys T, which must be in the dying state and must not be
- the running thread. */
-static void
-destroy_thread (struct thread *t)
-{
- ASSERT (is_thread (t));
- ASSERT (t->status == THREAD_DYING);
- ASSERT (t != thread_current ());
-
-#ifdef USERPROG
- addrspace_destroy (t);
-#endif
- palloc_free (t);
+ return list_entry (list_pop_front (&ready_list), struct thread, elem);
}
/* Completes a thread switch by activating the new thread's page
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
ASSERT (intr_get_level () == INTR_OFF);
+ /* Mark us as running. */
cur->status = THREAD_RUNNING;
#ifdef USERPROG
- addrspace_activate (cur);
+ /* Activate the new address space. */
+ process_activate ();
#endif
+ /* 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. */
if (prev != NULL && prev->status == THREAD_DYING)
- destroy_thread (prev);
+ {
+ ASSERT (prev != cur);
+ if (prev != initial_thread)
+ 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 schedule_tail() has
+ completed. */
static void
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;
+}
\f
/* Offset of `stack' member within `struct thread'.
Used by switch.S, which can't figure it out on its own. */