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This commit is as a result of a comment by Alan Cox (alc@cs.rice.edu)

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regarding the "real" problem with maps that we have been having
over the last few weeks.  He noted that the first_free pointer was
left dangling in certain circumstances -- and he was right!!!   This
should fix the map problems that we were having, and also give us the
advantage of being able to simplify maps more aggressively.
This commit is contained in:
John Dyson 1996-03-13 01:18:14 +00:00
parent b8d133e069
commit 308c24ba5e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=14610
1 changed files with 53 additions and 36 deletions
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89
sys/vm/vm_map.c
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@ -61,7 +61,7 @@
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*
* $Id: vm_map.c,v 1.37 1996/03/09 06:52:05 dyson Exp $
* $Id: vm_map.c,v 1.38 1996/03/12 13:46:13 dyson Exp $
*/
/*
@ -834,8 +834,8 @@ vm_map_simplify_entry(map, entry)
vm_map_t map;
vm_map_entry_t entry;
{
vm_map_entry_t next;
vm_size_t nextsize, esize;
vm_map_entry_t next, prev;
vm_size_t nextsize, prevsize, esize;
/*
* If this entry corresponds to a sharing map, then see if we can
@ -844,35 +844,55 @@ vm_map_simplify_entry(map, entry)
* neighbors.
*/
if (entry->is_sub_map)
if (entry->is_sub_map || entry->is_a_map || entry->wired_count)
return;
if (entry->is_a_map) {
return;
} else {
if (entry->wired_count)
return;
next = entry->next;
prev = entry->prev;
if (prev != &map->header) {
prevsize = prev->end - prev->start;
if ( prev->end == entry->start &&
prev->object.vm_object == entry->object.vm_object &&
prev->offset + prevsize == entry->offset &&
prev->protection == entry->protection &&
prev->max_protection == entry->max_protection &&
prev->inheritance == entry->inheritance &&
prev->needs_copy == entry->needs_copy &&
prev->copy_on_write == entry->copy_on_write &&
prev->is_a_map == FALSE &&
prev->is_sub_map == FALSE &&
prev->wired_count == 0) {
if (map->first_free == prev)
map->first_free = entry;
vm_map_entry_unlink(map, prev);
entry->start = prev->start;
entry->offset = prev->offset;
vm_object_deallocate(prev->object.vm_object);
vm_map_entry_dispose(map, prev);
}
}
next = entry->next;
if (next != &map->header) {
nextsize = next->end - next->start;
esize = entry->end - entry->start;
if (next != &map->header &&
entry->end == next->start &&
next->is_a_map == FALSE &&
next->is_sub_map == FALSE &&
next->object.vm_object == entry->object.vm_object &&
next->protection == entry->protection &&
next->max_protection == entry->max_protection &&
next->inheritance == entry->inheritance &&
next->needs_copy == entry->needs_copy &&
next->copy_on_write == entry->copy_on_write &&
entry->offset + esize == next->offset &&
next->wired_count == 0) {
vm_map_entry_unlink(map, next);
entry->end = next->end;
vm_object_deallocate(next->object.vm_object);
vm_map_entry_dispose(map, next);
}
if (entry->end == next->start &&
next->object.vm_object == entry->object.vm_object &&
entry->offset + esize == next->offset &&
next->protection == entry->protection &&
next->max_protection == entry->max_protection &&
next->inheritance == entry->inheritance &&
next->needs_copy == entry->needs_copy &&
next->copy_on_write == entry->copy_on_write &&
next->is_a_map == FALSE &&
next->is_sub_map == FALSE &&
next->wired_count == 0) {
if (map->first_free == next)
map->first_free = entry;
vm_map_entry_unlink(map, next);
entry->end = next->end;
vm_object_deallocate(next->object.vm_object);
vm_map_entry_dispose(map, next);
}
}
}
@ -2256,14 +2276,11 @@ vm_map_simplify(map, start)
) {
if (map->first_free == this_entry)
map->first_free = prev_entry;
if (!this_entry->object.vm_object->paging_in_progress) {
SAVE_HINT(map, prev_entry);
vm_map_entry_unlink(map, this_entry);
prev_entry->end = this_entry->end;
vm_object_deallocate(this_entry->object.vm_object);
vm_map_entry_dispose(map, this_entry);
}
SAVE_HINT(map, prev_entry);
vm_map_entry_unlink(map, this_entry);
prev_entry->end = this_entry->end;
vm_object_deallocate(this_entry->object.vm_object);
vm_map_entry_dispose(map, this_entry);
}
vm_map_unlock(map);
}