From: Mike Galbraith Date: Sat, 21 Jun 2014 10:09:48 +0200 Subject: memcontrol: Prevent scheduling while atomic in cgroup code Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.5-rt1.tar.xz 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 Signed-off-by: Mike Galbraith [bigeasy: use memcg_stock_ll as a locallock since it is now IRQ-off region] Signed-off-by: Sebastian Andrzej Siewior --- 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); } /*