The patch titled Subject: memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem() has been removed from the -mm tree. Its filename was memcg-add-rcu-locking-around-css_for_each_descendant_pre-in-memcg_offline_kmem.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Tejun Heo <tj@xxxxxxxxxx> Subject: memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem() memcg_offline_kmem() may be called from memcg_free_kmem() after a css init failure. memcg_free_kmem() is a ->css_free callback which is called without cgroup_mutex and memcg_offline_kmem() ends up using css_for_each_descendant_pre() without any locking. Fix it by adding rcu read locking around it. mkdir: cannot create directory `65530': No space left on device [ 527.241361] =============================== [ 527.241845] [ INFO: suspicious RCU usage. ] [ 527.242367] 4.6.0-work+ #321 Not tainted [ 527.242730] ------------------------------- [ 527.243220] kernel/cgroup.c:4008 cgroup_mutex or RCU read lock required! [ 527.243970] [ 527.243970] other info that might help us debug this: [ 527.243970] [ 527.244715] [ 527.244715] rcu_scheduler_active = 1, debug_locks = 0 [ 527.245463] 2 locks held by kworker/0:5/1664: [ 527.245939] #0: ("cgroup_destroy"){.+.+..}, at: [<ffffffff81060ab5>] process_one_work+0x165/0x4a0 [ 527.246958] #1: ((&css->destroy_work)#3){+.+...}, at: [<ffffffff81060ab5>] process_one_work+0x165/0x4a0 [ 527.248098] [ 527.248098] stack backtrace: [ 527.249565] CPU: 0 PID: 1664 Comm: kworker/0:5 Not tainted 4.6.0-work+ #321 [ 527.250429] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014 [ 527.250555] Workqueue: cgroup_destroy css_free_work_fn [ 527.250555] 0000000000000000 ffff880178747c68 ffffffff8128bfc7 ffff880178b8ac40 [ 527.250555] 0000000000000001 ffff880178747c98 ffffffff8108c297 0000000000000000 [ 527.250555] ffff88010de54138 000000000000fffb ffff88010de537e8 ffff880178747cc0 [ 527.250555] Call Trace: [ 527.250555] [<ffffffff8128bfc7>] dump_stack+0x68/0xa1 [ 527.250555] [<ffffffff8108c297>] lockdep_rcu_suspicious+0xd7/0x110 [ 527.250555] [<ffffffff810ca03d>] css_next_descendant_pre+0x7d/0xb0 [ 527.250555] [<ffffffff8114d14a>] memcg_offline_kmem.part.44+0x4a/0xc0 [ 527.250555] [<ffffffff8114d3ac>] mem_cgroup_css_free+0x1ec/0x200 [ 527.250555] [<ffffffff810ccdc9>] css_free_work_fn+0x49/0x5e0 [ 527.250555] [<ffffffff81060b15>] process_one_work+0x1c5/0x4a0 [ 527.250555] [<ffffffff81060ab5>] ? process_one_work+0x165/0x4a0 [ 527.250555] [<ffffffff81060e39>] worker_thread+0x49/0x490 [ 527.250555] [<ffffffff81060df0>] ? process_one_work+0x4a0/0x4a0 [ 527.250555] [<ffffffff81060df0>] ? process_one_work+0x4a0/0x4a0 [ 527.250555] [<ffffffff810672ba>] kthread+0xea/0x100 [ 527.250555] [<ffffffff814cbcff>] ret_from_fork+0x1f/0x40 [ 527.250555] [<ffffffff810671d0>] ? kthread_create_on_node+0x200/0x200 Link: http://lkml.kernel.org/r/20160526203018.GG23194@xxxxxxxxxxxxxxx Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Acked-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.5+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 3 +++ 1 file changed, 3 insertions(+) diff -puN mm/memcontrol.c~memcg-add-rcu-locking-around-css_for_each_descendant_pre-in-memcg_offline_kmem mm/memcontrol.c --- a/mm/memcontrol.c~memcg-add-rcu-locking-around-css_for_each_descendant_pre-in-memcg_offline_kmem +++ a/mm/memcontrol.c @@ -2896,6 +2896,7 @@ static void memcg_offline_kmem(struct me * ordering is imposed by list_lru_node->lock taken by * memcg_drain_all_list_lrus(). */ + rcu_read_lock(); /* can be called from css_free w/o cgroup_mutex */ css_for_each_descendant_pre(css, &memcg->css) { child = mem_cgroup_from_css(css); BUG_ON(child->kmemcg_id != kmemcg_id); @@ -2903,6 +2904,8 @@ static void memcg_offline_kmem(struct me if (!memcg->use_hierarchy) break; } + rcu_read_unlock(); + memcg_drain_all_list_lrus(kmemcg_id, parent->kmemcg_id); memcg_free_cache_id(kmemcg_id); _ Patches currently in -mm which might be from tj@xxxxxxxxxx are -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html