d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

o Add vm_map_wire() for wiring contiguous regions of either kernel

Browse Source 
or user vm_maps.  This implementation has two key benefits when compared
   to vm_map_{user_,}pageable(): (1) it avoids a race condition through
   the use of "in-transition" vm_map entries and (2) it eliminates lock
   recursion on the vm_map.

Note: there is still an error case that requires clean up.

Reviewed by:	tegge
This commit is contained in:
alc 2002-06-09 20:25:18 +00:00
parent 4ed3a69a51
commit 5dcd11e9ac
1 changed files with 159 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

160
sys/vm/vm_map.c
View File

@ -1621,8 +1621,166 @@ int
vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
boolean_t user_wire)
{
vm_map_entry_t entry, first_entry, tmp_entry;
vm_offset_t saved_end, saved_start;
unsigned int last_timestamp;
int rv;
boolean_t need_wakeup, result;
return (KERN_FAILURE);
vm_map_lock(map);
VM_MAP_RANGE_CHECK(map, start, end);
if (!vm_map_lookup_entry(map, start, &first_entry)) {
vm_map_unlock(map);
return (KERN_INVALID_ADDRESS);
}
last_timestamp = map->timestamp;
entry = first_entry;
while (entry != &map->header && entry->start < end) {
if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
/*
* We have not yet clipped the entry.
*/
saved_start = (start >= entry->start) ? start :
entry->start;
entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
if (vm_map_unlock_and_wait(map, user_wire)) {
/*
* Allow interruption of user wiring?
*/
}
vm_map_lock(map);
if (last_timestamp+1 != map->timestamp) {
/*
* Look again for the entry because the map was
* modified while it was unlocked.
* Specifically, the entry may have been
* clipped, merged, or deleted.
*/
if (!vm_map_lookup_entry(map, saved_start,
&tmp_entry)) {
if (saved_start == start) {
/*
* first_entry has been deleted.
*/
vm_map_unlock(map);
return (KERN_INVALID_ADDRESS);
}
end = saved_start;
rv = KERN_INVALID_ADDRESS;
goto done;
}
if (entry == first_entry)
first_entry = tmp_entry;
else
first_entry = NULL;
entry = tmp_entry;
}
last_timestamp = map->timestamp;
continue;
}
vm_map_clip_start(map, entry, start);
vm_map_clip_end(map, entry, end);
/*
* Mark the entry in case the map lock is released. (See
* above.)
*/
entry->eflags |= MAP_ENTRY_IN_TRANSITION;
/*
*
*/
if (entry->wired_count == 0) {
entry->wired_count++;
saved_start = entry->start;
saved_end = entry->end;
/*
* Release the map lock, relying on the in-transition
* mark.
*/
vm_map_unlock(map);
if (user_wire)
rv = vm_fault_user_wire(map, saved_start,
saved_end);
else
rv = vm_fault_wire(map, saved_start, saved_end);
vm_map_lock(map);
if (last_timestamp+1 != map->timestamp) {
/*
* Look again for the entry because the map was
* modified while it was unlocked. The entry
* may have been clipped, but NOT merged or
* deleted.
*/
result = vm_map_lookup_entry(map, saved_start,
&tmp_entry);
KASSERT(result, ("vm_map_wire: lookup failed"));
if (entry == first_entry)
first_entry = tmp_entry;
else
first_entry = NULL;
entry = tmp_entry;
while (entry->end < saved_end)
entry = entry->next;
}
last_timestamp = map->timestamp;
if (rv != KERN_SUCCESS) {
/*
* XXX
*/
end = entry->end;
goto done;
}
} else if (!user_wire ||
(entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
entry->wired_count++;
}
/*
* Check the map for holes in the specified region.
*/
if (entry->end < end && (entry->next == &map->header ||
entry->next->start > entry->end)) {
end = entry->end;
rv = KERN_INVALID_ADDRESS;
goto done;
}
entry = entry->next;
}
rv = KERN_SUCCESS;
done:
need_wakeup = FALSE;
if (first_entry == NULL) {
result = vm_map_lookup_entry(map, start, &first_entry);
KASSERT(result, ("vm_map_wire: lookup failed"));
}
entry = first_entry;
while (entry != &map->header && entry->start < end) {
if (rv == KERN_SUCCESS) {
if (user_wire)
entry->eflags |= MAP_ENTRY_USER_WIRED;
} else {
if (!user_wire || (entry->wired_count == 1 &&
(entry->eflags & MAP_ENTRY_USER_WIRED) == 0))
entry->wired_count--;
if (entry->wired_count == 0) {
/*
* Retain the map lock.
*/
vm_fault_unwire(map, entry->start, entry->end);
}
}
KASSERT(entry->eflags & MAP_ENTRY_IN_TRANSITION,
("vm_map_wire: in-transition flag missing"));
entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
need_wakeup = TRUE;
}
vm_map_simplify_entry(map, entry);
entry = entry->next;
}
vm_map_unlock(map);
if (need_wakeup)
vm_map_wakeup(map);
return (rv);
}
/*