patches/cgroups-scheduling-while-atomic-in-cgroup-code.patch

From: Mike Galbraith <umgwanakikbuti@gmail.com>
Date: Sat, 21 Jun 2014 10:09:48 +0200
Subject: memcontrol: Prevent scheduling while atomic in cgroup code

mm, memcg: make refill_stock() use get_cpu_light()

Nikita reported the following memcg scheduling while atomic bug:

Call Trace:
[e22d5a90] [c0007ea8] show_stack+0x4c/0x168 (unreliable)
[e22d5ad0] [c0618c04] __schedule_bug+0x94/0xb0
[e22d5ae0] [c060b9ec] __schedule+0x530/0x550
[e22d5bf0] [c060bacc] schedule+0x30/0xbc
[e22d5c00] [c060ca24] rt_spin_lock_slowlock+0x180/0x27c
[e22d5c70] [c00b39dc] res_counter_uncharge_until+0x40/0xc4
[e22d5ca0] [c013ca88] drain_stock.isra.20+0x54/0x98
[e22d5cc0] [c01402ac] __mem_cgroup_try_charge+0x2e8/0xbac
[e22d5d70] [c01410d4] mem_cgroup_charge_common+0x3c/0x70
[e22d5d90] [c0117284] __do_fault+0x38c/0x510
[e22d5df0] [c011a5f4] handle_pte_fault+0x98/0x858
[e22d5e50] [c060ed08] do_page_fault+0x42c/0x6fc
[e22d5f40] [c000f5b4] handle_page_fault+0xc/0x80

What happens:

   refill_stock()
      get_cpu_var()
      drain_stock()
         res_counter_uncharge()
            res_counter_uncharge_until()
               spin_lock() <== boom

Fix it by replacing get/put_cpu_var() with get/put_cpu_light().

Reported-by: Nikita Yushchenko <nyushchenko@dev.rtsoft.ru>
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
[bigeasy: use memcg_stock_ll as a locallock since it is now IRQ-off region]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 mm/memcontrol.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1685,6 +1685,7 @@ struct memcg_stock_pcp {
 #define FLUSHING_CACHED_CHARGE	0
 };
 static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
+static DEFINE_LOCAL_IRQ_LOCK(memcg_stock_ll);
 static DEFINE_MUTEX(percpu_charge_mutex);
 
 /**
@@ -1707,7 +1708,7 @@ static bool consume_stock(struct mem_cgr
 	if (nr_pages > CHARGE_BATCH)
 		return ret;
 
-	local_irq_save(flags);
+	local_lock_irqsave(memcg_stock_ll, flags);
 
 	stock = this_cpu_ptr(&memcg_stock);
 	if (memcg == stock->cached && stock->nr_pages >= nr_pages) {
@@ -1715,7 +1716,7 @@ static bool consume_stock(struct mem_cgr
 		ret = true;
 	}
 
-	local_irq_restore(flags);
+	local_unlock_irqrestore(memcg_stock_ll, flags);
 
 	return ret;
 }
@@ -1742,13 +1743,13 @@ static void drain_local_stock(struct wor
 	struct memcg_stock_pcp *stock;
 	unsigned long flags;
 
-	local_irq_save(flags);
+	local_lock_irqsave(memcg_stock_ll, flags);
 
 	stock = this_cpu_ptr(&memcg_stock);
 	drain_stock(stock);
 	clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
 
-	local_irq_restore(flags);
+	local_unlock_irqrestore(memcg_stock_ll, flags);
 }
 
 /*
@@ -1760,7 +1761,7 @@ static void refill_stock(struct mem_cgro
 	struct memcg_stock_pcp *stock;
 	unsigned long flags;
 
-	local_irq_save(flags);
+	local_lock_irqsave(memcg_stock_ll, flags);
 
 	stock = this_cpu_ptr(&memcg_stock);
 	if (stock->cached != memcg) { /* reset if necessary */
@@ -1769,7 +1770,7 @@ static void refill_stock(struct mem_cgro
 	}
 	stock->nr_pages += nr_pages;
 
-	local_irq_restore(flags);
+	local_unlock_irqrestore(memcg_stock_ll, flags);
 }
 
 /*