Imperial-MEng/pintos_22
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fix: properly assign frame owners and deallocate in all required places

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This commit is contained in:
Gleb Koval
2024-12-06 00:29:57 +00:00
parent 833c1b0520
commit 1da0c7d48c
5 changed files with 112 additions and 36 deletions
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100
src/vm/frame.c
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@@ -50,6 +50,8 @@ hash_less_func frame_metadata_less;
static struct list_elem *lru_next (struct list_elem *e);
static struct list_elem *lru_prev (struct list_elem *e);
static struct frame_metadata *get_victim (void);
static void free_owners (struct list *owners);
static struct frame_metadata *frame_metadata_find (void *frame);
/* Initialize the frame system by initializing the frame (hash) table with
the frame_metadata hashing and comparison functions, as well as initializing
@@ -95,15 +97,7 @@ frame_alloc (enum palloc_flags flags, void *upage, struct thread *owner)
page_insert_swapped (victim->upage, victim->frame, &victim->owners);
/* Free victim's owners. */
struct list_elem *oe;
for (oe = list_begin (&victim->owners);
oe != list_end (&victim->owners);)
{
struct frame_owner *frame_owner
= list_entry (oe, struct frame_owner, elem);
oe = list_remove (oe);
free (list_entry (oe, struct frame_owner, elem));
}
free_owners (&victim->owners);
/* If zero flag is set, zero out the victim page. */
if (flags & PAL_ZERO)
@@ -153,7 +147,6 @@ frame_alloc (enum palloc_flags flags, void *upage, struct thread *owner)
list_push_back (&frame_metadata->owners, &frame_owner->elem);
frame_metadata->upage = upage;
lock_release (&lru_lock);
return frame_metadata->frame;
}
@@ -163,18 +156,15 @@ frame_alloc (enum palloc_flags flags, void *upage, struct thread *owner)
void
frame_free (void *frame)
{
struct frame_metadata key_metadata;
key_metadata.frame = frame;
struct frame_metadata *frame_metadata = frame_metadata_find (frame);
if (frame_metadata == NULL)
PANIC ("Attempted to free a frame at kernel address %p, "
"but this address is not allocated!\n",
frame);
struct hash_elem *e =
hash_delete (&frame_table, &key_metadata.hash_elem);
if (e == NULL) PANIC ("Attempted to free a frame at kernel address %p, "
"but this address is not allocated!\n", frame);
struct frame_metadata *frame_metadata =
hash_entry (e, struct frame_metadata, hash_elem);
free_owners (&frame_metadata->owners);
lock_acquire (&lru_lock);
hash_delete (&frame_table, &frame_metadata->hash_elem);
list_remove (&frame_metadata->list_elem);
/* If we're freeing the frame marked as the next victim, update
@@ -193,6 +183,63 @@ frame_free (void *frame)
palloc_free_page (frame);
}
/* Add a thread to a frame's frame_metadata owners list. */
bool
frame_owner_insert (void *frame, struct thread *owner)
{
struct frame_metadata *frame_metadata = frame_metadata_find (frame);
if (frame_metadata == NULL)
return false;
struct frame_owner *frame_owner = malloc (sizeof (struct frame_owner));
if (frame_owner == NULL)
return false;
frame_owner->owner = owner;
list_push_back (&frame_metadata->owners, &frame_owner->elem);
return true;
}
/* Remove and deallocate a frame owner from the frame_metadata owners list.
*/
void
frame_owner_remove (void *frame, struct thread *owner)
{
struct frame_metadata *frame_metadata = frame_metadata_find (frame);
if (frame_metadata == NULL)
PANIC ("Attempted to remove an owner from a frame at kernel "
"address %p, but this address is not allocated!\n",
frame);
struct list_elem *oe;
for (oe = list_begin (&frame_metadata->owners);
oe != list_end (&frame_metadata->owners);)
{
struct frame_owner *frame_owner
= list_entry (oe, struct frame_owner, elem);
oe = list_next (oe);
if (frame_owner->owner == owner)
{
list_remove (&frame_owner->elem);
free (frame_owner);
return;
}
}
NOT_REACHED ();
}
/* Find a frame_metadata entry in the frame table. */
static struct frame_metadata *
frame_metadata_find (void *frame)
{
struct frame_metadata key_metadata;
key_metadata.frame = frame;
struct hash_elem *e = hash_find (&frame_table, &key_metadata.hash_elem);
if (e == NULL)
return NULL;
return hash_entry (e, struct frame_metadata, hash_elem);
}
/* TODO: Account for page aliases when checking accessed bit. */
/* A pre-condition for calling this function is that the calling thread
owns lru_lock and that lru_list is non-empty. */
@@ -230,6 +277,19 @@ get_victim (void)
return frame_metadata;
}
static void
free_owners (struct list *owners)
{
struct list_elem *oe;
for (oe = list_begin (owners); oe != list_end (owners);)
{
struct frame_owner *frame_owner
= list_entry (oe, struct frame_owner, elem);
oe = list_remove (oe);
free (frame_owner);
}
}
/* Hash function for frame metadata, used for storing entries in the
frame table. */
unsigned