[PATCH RESEND 1/3] memcg: mm_update_next_owner() should skip kthreads

[Oleg Nesterov <oleg@redhat.com>]

"Search through everything else" in mm_update_next_owner() can
hit a kthread which adopted this "mm" via use_mm(), it should
not be used as mm->owner. Add the PF_KTHREAD check.

While at it, change this code to use for_each_process_thread()
instead of deprecated do_each_thread/while_each_thread.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
---
 kernel/exit.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index ad7183a..e270d2a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -356,14 +356,12 @@ retry:
 	}
 
 	/*
-	 * Search through everything else. We should not get
-	 * here often
+	 * Search through everything else, we should not get here often.
 	 */
-	do_each_thread(g, c) {
-		if (c->mm == mm)
+	for_each_process_thread(g, c) {
+		if (!(c->flags & PF_KTHREAD) && c->mm == mm)
 			goto assign_new_owner;
-	} while_each_thread(g, c);
-
+	}
 	read_unlock(&tasklist_lock);
 	/*
 	 * We found no owner yet mm_users > 1: this implies that we are
-- 
1.5.5.1