Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933175AbaFUIJ6 (ORCPT ); Sat, 21 Jun 2014 04:09:58 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:49957 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758051AbaFUIJx (ORCPT ); Sat, 21 Jun 2014 04:09:53 -0400 Message-ID: <1403338188.6766.6.camel@marge.simpson.net> Subject: Re: [v3.10-rt / v3.12-rt] scheduling while atomic in cgroup code From: Mike Galbraith To: Nikita Yushchenko Cc: linux-rt-users@vger.kernel.org, "'Alexey Lugovskoy'" , Konstantin Kholopov , linux-kernel@vger.kernel.org, Steven Rostedt Date: Sat, 21 Jun 2014 10:09:48 +0200 In-Reply-To: <53A50218.6020506@dev.rtsoft.ru> References: <53A50218.6020506@dev.rtsoft.ru> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2014-06-21 at 07:55 +0400, Nikita Yushchenko wrote: > Hi. > > 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() calls get_cpu_var() and thus disables preemption until > matching put_cpu_var() is called, > > - then it calls drain_stock() -> res_counter_uncharge() -> > res_counter_uncharge_until() > > - and here we have spin_lock(), which under RT can sleep. Thus we have > sleeping with preemption disabled. > > > Any ideas how to fix? The below should work.. though not as well as turning it off. mm, memcg: make refill_stock()/consume_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 --- mm/memcontrol.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2398,16 +2398,18 @@ static bool consume_stock(struct mem_cgr { struct memcg_stock_pcp *stock; bool ret = true; + int cpu; if (nr_pages > CHARGE_BATCH) return false; - stock = &get_cpu_var(memcg_stock); + cpu = get_cpu_light(); + stock = &per_cpu(memcg_stock, cpu); if (memcg == stock->cached && stock->nr_pages >= nr_pages) stock->nr_pages -= nr_pages; else /* need to call res_counter_charge */ ret = false; - put_cpu_var(memcg_stock); + put_cpu_light(); return ret; } @@ -2457,14 +2459,17 @@ static void __init memcg_stock_init(void */ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { - struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock); + struct memcg_stock_pcp *stock; + int cpu = get_cpu_light(); + + stock = &per_cpu(memcg_stock, cpu); if (stock->cached != memcg) { /* reset if necessary */ drain_stock(stock); stock->cached = memcg; } stock->nr_pages += nr_pages; - put_cpu_var(memcg_stock); + put_cpu_light(); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/