mm owner: fix race between swapoff and exit

[safe/jmp/linux-2.6] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 13932ab..a0123d7 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2738,14 +2738,15 @@ void cgroup_fork_callbacks(struct task_struct *child)
  */
 void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
 {
-       struct cgroup *oldcgrp, *newcgrp;
+       struct cgroup *oldcgrp, *newcgrp = NULL;
 
        if (need_mm_owner_callback) {
                int i;
                for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                        struct cgroup_subsys *ss = subsys[i];
                        oldcgrp = task_cgroup(old, ss->subsys_id);
-                       newcgrp = task_cgroup(new, ss->subsys_id);
+                       if (new)
+                               newcgrp = task_cgroup(new, ss->subsys_id);
                        if (oldcgrp == newcgrp)
                                continue;
                        if (ss->mm_owner_changed)