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

From: Oleg Nesterov
Date: Fri Apr 02 2010 - 14:34:46 EST

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@xxxxxxxxxx>

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);

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/