-Index: threads/synch.c
+Index: src/threads/synch.c
===================================================================
-RCS file: /u/blp/cvs/pintos/src/threads/synch.c,v
-retrieving revision 1.14
-diff -u -p -u -r1.14 synch.c
---- threads/synch.c 29 Sep 2004 01:04:09 -0000 1.14
-+++ threads/synch.c 11 Oct 2004 07:29:34 -0000
-@@ -89,10 +89,32 @@ sema_up (struct semaphore *sema)
+RCS file: /afs/ir.stanford.edu/users/b/l/blp/private/cvs/pintos/src/threads/synch.c,v
+retrieving revision 1.15
+diff -u -p -u -r1.15 synch.c
+--- src/threads/synch.c 31 Dec 2004 21:13:38 -0000 1.15
++++ src/threads/synch.c 31 Dec 2004 22:31:03 -0000
+@@ -77,6 +77,17 @@ sema_down (struct semaphore *sema)
+ intr_set_level (old_level);
+ }
+
++/* Returns true if thread A has lower priority than thread B. */
++static bool
++donated_lower_priority (const list_elem *a_, const list_elem *b_,
++ void *aux UNUSED)
++{
++ const struct thread *a = list_entry (a_, struct thread, donor_elem);
++ const struct thread *b = list_entry (b_, struct thread, donor_elem);
++
++ return a->priority < b->priority;
++}
++
+ /* Up or "V" operation on a semaphore. Increments SEMA's value
+ and wakes up one thread of those waiting for SEMA, if any.
+
+@@ -89,10 +100,28 @@ sema_up (struct semaphore *sema)
ASSERT (sema != NULL);
old_level = intr_disable ();
sema->value++;
+ if (!list_empty (&sema->waiters))
+ {
-+ struct thread *max;
-+ list_elem *e;
++ /* Find highest-priority waiting thread. */
++ struct thread *max = list_entry (list_max (&sema->waiters,
++ donated_lower_priority, NULL),
++ struct thread, elem);
+
-+ max = list_entry (list_front (&sema->waiters), struct thread, elem);
-+ for (e = list_begin (&sema->waiters);
-+ e != list_end (&sema->waiters); e = list_next (e))
-+ {
-+ struct thread *t = list_entry (e, struct thread, elem);
-+ if (t->priority > max->priority)
-+ max = t;
-+ }
++ /* Remove `max' from wait list and unblock. */
+ list_remove (&max->elem);
+ thread_unblock (max);
+
-+ /* Kind of a funny interaction with donation here.
++ /* Yield to a higher-priority thread, if we're running in a
++ context where it makes sense to do so.
++
++ Kind of a funny interaction with donation here.
+ We only support donation for locks, and locks turn off
+ interrupts before calling us, so we automatically don't
+ do the yield here, delegating to lock_release(). */
-+ if (!intr_context ()
-+ && max->priority > thread_get_priority ()
-+ && old_level == INTR_ON)
-+ thread_yield ();
++ if (!intr_context () && old_level == INTR_ON)
++ thread_yield_to_higher_priority ();
+ }
intr_set_level (old_level);
}
-@@ -166,6 +188,21 @@ lock_init (struct lock *lock, const char
- sema_init (&lock->semaphore, 1, name);
- }
-
-+static void
-+revise_priority (struct thread *t)
-+{
-+ list_elem *e;
-+
-+ t->priority = t->normal_priority;
-+ for (e = list_begin (&t->donors); e != list_end (&t->donors);
-+ e = list_next (e))
-+ {
-+ struct thread *donor = list_entry (e, struct thread, donor_elem);
-+ if (donor->priority > t->priority)
-+ t->priority = donor->priority;
-+ }
-+}
-+
- /* Acquires LOCK, sleeping until it becomes available if
- necessary. The lock must not already be held by the current
- thread.
-@@ -184,6 +221,17 @@ lock_acquire (struct lock *lock)
+@@ -184,6 +213,23 @@ lock_acquire (struct lock *lock)
ASSERT (!lock_held_by_current_thread (lock));
old_level = intr_disable ();
+
+ if (lock->holder != NULL)
+ {
++ /* Donate our priority to the thread holding the lock.
++ First, update the data structures. */
+ struct thread *donor = thread_current ();
+ donor->want_lock = lock;
+ donor->donee = lock->holder;
+ list_push_back (&lock->holder->donors, &donor->donor_elem);
-+ revise_priority (lock->holder);
-+ //recurse_donation (&lock->holder);
++
++ /* Now implement the priority donation itself
++ by recomputing the donee's priority
++ and cascading the donation as far as necessary. */
++ while (donor->donee != NULL && thread_recompute_priority (donor->donee))
++ donor = donor->donee;
+ }
+
sema_down (&lock->semaphore);
lock->holder = thread_current ();
intr_set_level (old_level);
-@@ -198,13 +246,32 @@ void
+@@ -198,13 +244,38 @@ void
lock_release (struct lock *lock)
{
enum intr_level old_level;
+ struct thread *t = thread_current ();
-+ list_elem *e, *next;
-+ bool did_donate = false;
++ list_elem *e;
ASSERT (lock != NULL);
ASSERT (lock_held_by_current_thread (lock));
old_level = intr_disable ();
-+ for (e = list_begin (&t->donors); e != list_end (&t->donors);
-+ e = next)
++
++ /* Remove donations from threads that want the lock we're
++ releasing. */
++ for (e = list_begin (&t->donors); e != list_end (&t->donors); )
+ {
+ struct thread *donor = list_entry (e, struct thread, donor_elem);
-+ next = list_next (e);
+ if (donor->want_lock == lock)
+ {
+ donor->donee = NULL;
-+ list_remove (e);
-+ did_donate = true;
++ e = list_remove (e);
+ }
++ else
++ e = list_next (e);
+ }
-+ revise_priority (t);
++
++ /* Release lock. */
lock->holder = NULL;
-+
sema_up (&lock->semaphore);
-+ if (did_donate)
-+ thread_yield ();
++
++ /* Recompute our priority based on our remaining donations,
++ then yield to a higher-priority ready thread if one now
++ exists. */
++ thread_recompute_priority (t);
++ thread_yield_to_higher_priority ();
++
intr_set_level (old_level);
}
-diff -u -p -u -p -r1.48 thread.c
---- threads/thread.c 9 Oct 2004 18:01:37 -0000 1.48
-+++ threads/thread.c 14 Oct 2004 05:21:08 -0000
+Index: src/threads/thread.c
+===================================================================
+RCS file: /afs/ir.stanford.edu/users/b/l/blp/private/cvs/pintos/src/threads/thread.c,v
+retrieving revision 1.48
+diff -u -p -u -r1.48 thread.c
+--- src/threads/thread.c 9 Oct 2004 18:01:37 -0000 1.48
++++ src/threads/thread.c 31 Dec 2004 22:31:03 -0000
@@ -166,6 +166,8 @@ thread_create (const char *name, int pri
/* Add to run queue. */
return tid;
}
-@@ -186,6 +188,16 @@ thread_block (void)
+@@ -186,6 +188,18 @@ thread_block (void)
schedule ();
}
++/* Returns true if A has higher priority than B,
++ within a list of threads. */
+static bool
-+thread_greater_priority (const list_elem *a_, const list_elem *b_,
-+ void *aux UNUSED)
++thread_higher_priority (const list_elem *a_, const list_elem *b_,
++ void *aux UNUSED)
+{
+ const struct thread *a = list_entry (a_, struct thread, elem);
+ const struct thread *b = list_entry (b_, struct thread, elem);
/* 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.) */
-@@ -198,7 +210,7 @@ thread_unblock (struct thread *t)
+@@ -198,7 +212,7 @@ thread_unblock (struct thread *t)
old_level = intr_disable ();
ASSERT (t->status == THREAD_BLOCKED);
- list_push_back (&ready_list, &t->elem);
-+ list_insert_ordered (&ready_list, &t->elem, thread_greater_priority, NULL);
++ list_insert_ordered (&ready_list, &t->elem, thread_higher_priority, NULL);
t->status = THREAD_READY;
intr_set_level (old_level);
}
-@@ -266,11 +278,44 @@ thread_yield (void)
+@@ -266,11 +280,79 @@ thread_yield (void)
ASSERT (!intr_context ());
old_level = intr_disable ();
- list_push_back (&ready_list, &cur->elem);
-+ list_insert_ordered (&ready_list, &cur->elem, thread_greater_priority, NULL);
++ list_insert_ordered (&ready_list, &cur->elem, thread_higher_priority, NULL);
cur->status = THREAD_READY;
schedule ();
intr_set_level (old_level);
}
+
++/* Sets the current thread's priority to PRIORITY. */
+void
+thread_set_priority (int priority)
+{
+ struct thread *t = thread_current ();
-+ int old_priority, new_priority;
-+ list_elem *e;
++ enum intr_level old_level;
+
-+ old_priority = t->priority;
-+ new_priority = t->normal_priority = priority;
-+ for (e = list_begin (&t->donors); e != list_end (&t->donors);
-+ e = list_next (e))
-+ {
-+ struct thread *donor = list_entry (e, struct thread, donor_elem);
-+ if (donor->priority > t->priority)
-+ new_priority = donor->priority;
-+ }
++ t->normal_priority = priority;
+
-+ t->priority = new_priority;
-+
-+ if (new_priority < old_priority)
-+ {
-+ /* FIXME: if this is still (one of) the highest priority
-+ threads then don't yield. */
-+ thread_yield ();
-+ }
++ old_level = intr_disable ();
++ while (thread_recompute_priority (t) && t->donee != NULL)
++ t = t->donee;
++ thread_yield_to_higher_priority ();
++ intr_set_level (old_level);
+}
+
++/* Returns the current thread's priority. */
+int
+thread_get_priority (void)
+{
+ return thread_current ()->priority;
++}
++
++/* Returns true if thread A has lower priority than thread B,
++ within a list of donors. */
++static bool
++donated_lower_priority (const list_elem *a_, const list_elem *b_,
++ void *aux UNUSED)
++{
++ const struct thread *a = list_entry (a_, struct thread, donor_elem);
++ const struct thread *b = list_entry (b_, struct thread, donor_elem);
++
++ return a->priority < b->priority;
++}
++
++/* Recomputes T's priority in terms of its normal priority and
++ its donors' priorities, if any.
++ Returns true if T's new priority is higher than its old
++ priority, false otherwise. */
++bool
++thread_recompute_priority (struct thread *t)
++{
++ int old = t->priority;
++ int donation = 0;
++ if (!list_empty (&t->donors))
++ donation = list_entry (list_max (&t->donors, donated_lower_priority, NULL),
++ struct thread, donor_elem)->priority;
++ t->priority = donation > t->normal_priority ? donation : t->normal_priority;
++ return t->priority > old;
++}
++
++/* If the ready list contains a thread with a higher priority,
++ yields to it. */
++void
++thread_yield_to_higher_priority (void)
++{
++ enum intr_level old_level = intr_disable ();
++ if (!list_empty (&ready_list))
++ {
++ struct thread *cur = thread_current ();
++ struct thread *max = list_entry (list_front (&ready_list),
++ struct thread, elem);
++ if (max->priority > cur->priority)
++ thread_yield ();
++ }
++ intr_set_level (old_level);
+}
\f
/* Idle thread. Executes when no other thread is ready to run. */
static void
-@@ -335,8 +380,9 @@ init_thread (struct thread *t, const cha
+@@ -335,8 +417,9 @@ init_thread (struct thread *t, const cha
t->status = THREAD_BLOCKED;
strlcpy (t->name, name, sizeof t->name);
t->stack = (uint8_t *) t + PGSIZE;
}
/* Allocates a SIZE-byte frame at the top of thread T's stack and
-Index: threads/thread.h
+Index: src/threads/thread.h
===================================================================
-RCS file: /u/blp/cvs/pintos/src/threads/thread.h,v
+RCS file: /afs/ir.stanford.edu/users/b/l/blp/private/cvs/pintos/src/threads/thread.h,v
retrieving revision 1.28
diff -u -p -u -r1.28 thread.h
---- threads/thread.h 29 Sep 2004 01:04:20 -0000 1.28
-+++ threads/thread.h 11 Oct 2004 07:29:35 -0000
-@@ -88,6 +88,13 @@ struct thread
+--- src/threads/thread.h 29 Sep 2004 01:04:20 -0000 1.28
++++ src/threads/thread.h 31 Dec 2004 22:31:03 -0000
+@@ -87,7 +87,14 @@ struct thread
+ enum thread_status status; /* Thread state. */
char name[16]; /* Name (for debugging purposes). */
uint8_t *stack; /* Saved stack pointer. */
- int priority; /* Priority. */
-+ int normal_priority; /* Priority. */
+- int priority; /* Priority. */
+
-+ /* Priority donation. */
-+ struct list donors;
-+ list_elem donor_elem;
-+ struct thread *donee;
-+ struct lock *want_lock;
++ /* Thread priority. */
++ int priority; /* Priority, including donations. */
++ int normal_priority; /* Priority, without donations. */
++ struct list donors; /* Threads donating priority to us. */
++ list_elem donor_elem; /* Element in donors list. */
++ struct thread *donee; /* Thread we're donating to. */
++ struct lock *want_lock; /* Lock we're waiting to acquire. */
/* Shared between thread.c and synch.c. */
list_elem elem; /* List element. */
+@@ -118,6 +125,8 @@ const char *thread_name (void);
+
+ void thread_exit (void) NO_RETURN;
+ void thread_yield (void);
++void thread_yield_to_higher_priority (void);
++bool thread_recompute_priority (struct thread *);
+
+ /* This function will be implemented in problem 1-2. */
+ void thread_join (tid_t);
projects / pintos-anon / commitdiff