Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754164Ab0DWDSb (ORCPT ); Thu, 22 Apr 2010 23:18:31 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:34464 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751611Ab0DWDSZ (ORCPT ); Thu, 22 Apr 2010 23:18:25 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Fri, 23 Apr 2010 12:14:24 +0900 From: KAMEZAWA Hiroyuki To: Li Zefan Cc: Balbir Singh , Daisuke Nishimura , "Paul E. McKenney" , "linux-mm@kvack.org" , LKML , "akpm@linux-foundation.org" Subject: [BUGFIX][PATCH] memcg rcu lock fix in swap code (Was Re: [BUG] an RCU warning in memcg Message-Id: <20100423121424.ae47efcb.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <4BD10D59.9090504@cn.fujitsu.com> References: <4BD10D59.9090504@cn.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.2 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2926 Lines: 84 On Fri, 23 Apr 2010 11:00:41 +0800 Li Zefan wrote: > with CONFIG_PROVE_RCU=y, I saw this warning, it's because > css_id() is not under rcu_read_lock(). > Ok. Thank you for reporting. This is ok ? == From: KAMEZAWA Hiroyuki css_id() should be called under rcu_read_lock(). Following is a report from Li Zefan. == =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/cgroup.c:4438 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 1 lock held by kswapd0/31: #0: (swap_lock){+.+.-.}, at: [] swap_info_get+0x4b/0xd0 stack backtrace: Pid: 31, comm: kswapd0 Not tainted 2.6.34-rc5-tip+ #13 Call Trace: [] ? printk+0x1d/0x1f [] lockdep_rcu_dereference+0x94/0xb0 [] css_id+0x5d/0x60 [] mem_cgroup_uncharge_swapcache+0x45/0xa0 [] swapcache_free+0x3f/0x60 [] __remove_mapping+0xb2/0xf0 [] shrink_page_list+0x26b/0x490 [] ? put_lock_stats+0xd/0x30 [] ? _raw_spin_unlock_irq+0x27/0x50 [] ? trace_hardirqs_on_caller+0xb6/0x220 [] shrink_inactive_list+0x278/0x620 [] ? sched_clock_cpu+0x121/0x180 [] ? trace_hardirqs_off_caller+0x18/0x130 [] ? trace_hardirqs_off+0xb/0x10 [] ? sub_preempt_count+0x8/0x90 [] ? put_lock_stats+0xd/0x30 [] shrink_zone+0x204/0x3c0 [] ? _raw_spin_unlock+0x2c/0x50 [] kswapd+0x61e/0x7c0 [] ? isolate_pages_global+0x0/0x1f0 [] ? autoremove_wake_function+0x0/0x50 [] ? kswapd+0x0/0x7c0 [] kthread+0x74/0x80 [] ? kthread+0x0/0x80 [] kernel_thread_helper+0x6/0x10 Reported-by: Li Zefan Cc: Daisuke Nishimura Cc: Balbir Singh Signed-off-by: KAMEZAWA Hiroyuki --- mm/memcontrol.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6.34-rc5-mm1/mm/memcontrol.c =================================================================== --- linux-2.6.34-rc5-mm1.orig/mm/memcontrol.c +++ linux-2.6.34-rc5-mm1/mm/memcontrol.c @@ -2401,7 +2401,9 @@ mem_cgroup_uncharge_swapcache(struct pag /* record memcg information */ if (do_swap_account && swapout && memcg) { + rcu_read_lock(); swap_cgroup_record(ent, css_id(&memcg->css)); + rcu_read_unlock(); mem_cgroup_get(memcg); } if (swapout && memcg) -- 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/