[PATCH -mm 2/4] oom: select_bad_process: PF_EXITING check should take ->mm into account

[Oleg Nesterov <oleg@redhat.com>]

select_bad_process() checks PF_EXITING to detect the task which
is going to release its memory, but the logic is very wrong.

	- a single process P with the dead group leader disables
	  select_bad_process() completely, it will always return
	  ERR_PTR() while P can live forever

	- if the PF_EXITING task has already released its ->mm
	  it doesn't make sense to expect it is goiing to free
	  more memory (except task_struct/etc)

Change the code to ignore the PF_EXITING tasks without ->mm.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 mm/oom_kill.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- MM/mm/oom_kill.c~2_FIX_PF_EXITING	2010-04-02 18:51:05.000000000 +0200
+++ MM/mm/oom_kill.c	2010-04-02 18:58:37.000000000 +0200
@@ -322,7 +322,7 @@ static struct task_struct *select_bad_pr
 		 * the process of exiting and releasing its resources.
 		 * Otherwise we could get an easy OOM deadlock.
 		 */
-		if (p->flags & PF_EXITING) {
+		if ((p->flags & PF_EXITING) && p->mm) {
 			if (p != current)
 				return ERR_PTR(-1UL);