- When the VM daemon is out of swap space and looking for a

  process to kill, don't block on a map lock while holding the
  process lock.  Instead, skip processes whose map locks are held
  and find something else to kill.
- Add vm_map_trylock_read() to support the above.

Reviewed by:	alc, mike (mentor)

1 files changed, 7 insertions, 2 deletions

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 8e3c39f..dab4ae2 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1214,8 +1214,13 @@ rescan0:
 			/*
 			 * get the process size
 			 */
-			size = vmspace_resident_count(p->p_vmspace) +
-				vmspace_swap_count(p->p_vmspace);
+			if (!vm_map_trylock_read(&p->p_vmspace->vm_map)) {
+				PROC_UNLOCK(p);
+				continue;
+			}
+			size = vmspace_swap_count(p->p_vmspace);
+			vm_map_unlock_read(&p->p_vmspace->vm_map);
+			size += vmspace_resident_count(p->p_vmspace);
 			/*
 			 * if the this process is bigger than the biggest one
 			 * remember it.