#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/process.h"
#endif
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;
#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 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
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)
{
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 ();
void
thread_start (void)
{
- thread_create ("idle", PRI_MAX, 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. */
+/* Called by the timer interrupt handler at each timer tick.
+ Thus, this function runs in an external interrupt context. */
void
thread_tick (void)
{
struct switch_entry_frame *ef;
struct switch_threads_frame *sf;
tid_t tid;
+ enum intr_level old_level;
ASSERT (function != NULL);
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;
/* 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);
/* 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)
{
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 ();
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);
}
+/* 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)
return 0;
}
\f
-/* 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 (;;)
{
one to occur, wasting as much as one clock tick worth of
time.
- See [IA32-v2a] "HLT", [IA32-v2b] "STI", and [IA32-v3] 7.7. */
- asm ("sti; hlt");
+ See [IA32-v2a] "HLT", [IA32-v2b] "STI", and [IA32-v3a]
+ 7.11.1 "HLT Instruction". */
+ asm volatile ("sti; hlt" : : : "memory");
}
}
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);
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
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 ();
/* 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)
+ 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);
- if (prev != initial_thread)
- palloc_free_page (prev);
+ palloc_free_page (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)
{
if (cur != next)
prev = switch_threads (cur, next);
- schedule_tail (prev);
+ thread_schedule_tail (prev);
}
/* Returns a tid to use for a new thread. */
projects / pintos-anon / blobdiff