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

Fix a long standing (from the original 4.4BSD lite sources) race between

Browse Source 
vmspace_fork and vm_map_wire that would lead to "vm_fault_copy_wired: page
missing" panics.  While faulting in pages for a map entry that is being
wired down, mark the containing map as busy.  In vmspace_fork wait until the
map is unbusy, before we try to copy the entries.

Reviewed by:	kib
MFC after:	5 days
Sponsored by:	Isilon Systems, Inc.
This commit is contained in:
mlaier 2010-12-09 21:02:22 +00:00
parent c3ffedd66b
commit da2dde653e
2 changed files with 46 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
sys/vm/vm_map.c
View File

@ -671,6 +671,41 @@ vm_map_wakeup(vm_map_t map)
wakeup(&map->root);
}
void
vm_map_busy(vm_map_t map)
{
VM_MAP_ASSERT_LOCKED(map);
map->busy++;
}
void
vm_map_unbusy(vm_map_t map)
{
VM_MAP_ASSERT_LOCKED(map);
KASSERT(map->busy, ("vm_map_unbusy: not busy"));
if (--map->busy == 0 && (map->flags & MAP_BUSY_WAKEUP)) {
vm_map_modflags(map, 0, MAP_BUSY_WAKEUP);
wakeup(&map->busy);
}
}
void
vm_map_wait_busy(vm_map_t map)
{
VM_MAP_ASSERT_LOCKED(map);
while (map->busy) {
vm_map_modflags(map, MAP_BUSY_WAKEUP, 0);
if (map->system_map)
msleep(&map->busy, &map->system_mtx, 0, "mbusy", 0);
else
sx_sleep(&map->busy, &map->lock, 0, "mbusy", 0);
}
map->timestamp++;
}
long
vmspace_resident_count(struct vmspace *vmspace)
{
@ -718,6 +753,7 @@ _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
map->flags = 0;
map->root = NULL;
map->timestamp = 0;
map->busy = 0;
}
void
@ -2382,12 +2418,14 @@ vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
entry->object.vm_object->type == OBJT_SG);
/*
* Release the map lock, relying on the in-transition
* mark.
* mark. Mark the map busy for fork.
*/
vm_map_busy(map);
vm_map_unlock(map);
rv = vm_fault_wire(map, saved_start, saved_end,
fictitious);
vm_map_lock(map);
vm_map_unbusy(map);
if (last_timestamp + 1 != map->timestamp) {
/*
* Look again for the entry because the map was
@ -2995,6 +3033,8 @@ vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_charge)
int locked;
vm_map_lock(old_map);
if (old_map->busy)
vm_map_wait_busy(old_map);
vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
if (vm2 == NULL)
goto unlock_and_return;

5
sys/vm/vm_map.h
View File

@ -187,12 +187,14 @@ struct vm_map {
pmap_t pmap; /* (c) Physical map */
#define min_offset header.start /* (c) */
#define max_offset header.end /* (c) */
int busy;
};
/*
* vm_flags_t values
*/
#define MAP_WIREFUTURE 0x01 /* wire all future pages */
#define MAP_BUSY_WAKEUP 0x02
#ifdef _KERNEL
static __inline vm_offset_t
@ -275,6 +277,9 @@ int _vm_map_lock_upgrade(vm_map_t map, const char *file, int line);
void _vm_map_lock_downgrade(vm_map_t map, const char *file, int line);
int vm_map_locked(vm_map_t map);
void vm_map_wakeup(vm_map_t map);
void vm_map_busy(vm_map_t map);
void vm_map_unbusy(vm_map_t map);
void vm_map_wait_busy(vm_map_t map);
#define vm_map_lock(map) _vm_map_lock(map, LOCK_FILE, LOCK_LINE)
#define vm_map_unlock(map) _vm_map_unlock(map, LOCK_FILE, LOCK_LINE)