rt-patches/0250-memcontrol-Prevent-scheduling-while-atomic-in-cgroup.patch

   1 From 4f1f6257ddad8645baa9b2c00b7920137e4d7f6b Mon Sep 17 00:00:00 2001
   2 From: Mike Galbraith <umgwanakikbuti@gmail.com>
   3 Date: Sat, 21 Jun 2014 10:09:48 +0200
   4 Subject: [PATCH 250/366] memcontrol: Prevent scheduling while atomic in cgroup
   5  code
   6
   7 mm, memcg: make refill_stock() use get_cpu_light()
   8
   9 Nikita reported the following memcg scheduling while atomic bug:
  10
  11 Call Trace:
  12 [e22d5a90] [c0007ea8] show_stack+0x4c/0x168 (unreliable)
  13 [e22d5ad0] [c0618c04] __schedule_bug+0x94/0xb0
  14 [e22d5ae0] [c060b9ec] __schedule+0x530/0x550
  15 [e22d5bf0] [c060bacc] schedule+0x30/0xbc
  16 [e22d5c00] [c060ca24] rt_spin_lock_slowlock+0x180/0x27c
  17 [e22d5c70] [c00b39dc] res_counter_uncharge_until+0x40/0xc4
  18 [e22d5ca0] [c013ca88] drain_stock.isra.20+0x54/0x98
  19 [e22d5cc0] [c01402ac] __mem_cgroup_try_charge+0x2e8/0xbac
  20 [e22d5d70] [c01410d4] mem_cgroup_charge_common+0x3c/0x70
  21 [e22d5d90] [c0117284] __do_fault+0x38c/0x510
  22 [e22d5df0] [c011a5f4] handle_pte_fault+0x98/0x858
  23 [e22d5e50] [c060ed08] do_page_fault+0x42c/0x6fc
  24 [e22d5f40] [c000f5b4] handle_page_fault+0xc/0x80
  25
  26 What happens:
  27
  28    refill_stock()
  29       get_cpu_var()
  30       drain_stock()
  31          res_counter_uncharge()
  32             res_counter_uncharge_until()
  33                spin_lock() <== boom
  34
  35 Fix it by replacing get/put_cpu_var() with get/put_cpu_light().
  36
  37 Reported-by: Nikita Yushchenko <nyushchenko@dev.rtsoft.ru>
  38 Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
  39 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  40 ---
  41  mm/memcontrol.c | 7 +++++--
  42  1 file changed, 5 insertions(+), 2 deletions(-)
  43
  44 diff --git a/mm/memcontrol.c b/mm/memcontrol.c
  45 index 8e5dc27..82cc68b 100644
  46 --- a/mm/memcontrol.c
  47 +++ b/mm/memcontrol.c
  48 @@ -1925,14 +1925,17 @@ static void drain_local_stock(struct work_struct *dummy)
  49   */
  50  static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
  51  {
  52 -       struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
  53 +       struct memcg_stock_pcp *stock;
  54 +       int cpu = get_cpu_light();
  55 +
  56 +       stock = &per_cpu(memcg_stock, cpu);
  57
  58         if (stock->cached != memcg) { /* reset if necessary */
  59                 drain_stock(stock);
  60                 stock->cached = memcg;
  61         }
  62         stock->nr_pages += nr_pages;
  63 -       put_cpu_var(memcg_stock);
  64 +       put_cpu_light();
  65  }
  66
  67  /*
  68 --
  69 1.9.1
  70