From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935154Ab3BOABn (ORCPT ); Thu, 14 Feb 2013 19:01:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44012 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935101Ab3BOABm (ORCPT ); Thu, 14 Feb 2013 19:01:42 -0500 Message-ID: <511D7ADA.7040104@redhat.com> Date: Fri, 15 Feb 2013 00:01:30 +0000 From: Andrew Price User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Steven Whitehouse , Dipankar Sarma , linux-kernel@vger.kernel.org, adas@redhat.com, hch@lst.de, npiggin@gmail.com Subject: Re: rcu: fix hlist_bl_set_first_rcu annotation References: <1359572877.2719.50.camel@menhir> <20130203183958.GO2632@linux.vnet.ibm.com> In-Reply-To: <20130203183958.GO2632@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 03/02/13 18:39, Paul E. McKenney wrote: > On Wed, Jan 30, 2013 at 07:07:57PM +0000, Steven Whitehouse wrote: >> >> Abhi noticed that we were getting a complaint from the RCU subsystem >> about access of an RCU protected list under the write side bit lock. >> This patch adds additional annotation to check both the RCU read >> lock and the write side bit lock before printing a message. >> >> Signed-off-by: Steven Whitehouse >> Reported-by: Abhijith Das >> Tested-by: Abhijith Das > > Looks plausible to me on first glance, copying Nick Piggin and Christoph > Hellwig. If they have no objections, I will queue this. > > Thanx, Paul Has this had any attention yet? I'm also seeing the complaint quite frequently: [ 68.738811] =============================== [ 68.741380] [ INFO: suspicious RCU usage. ] [ 68.748785] 3.8.0-0.rc7.git1.1.fc19.x86_64 #1 Not tainted [ 68.750841] ------------------------------- [ 68.752418] include/linux/rculist_bl.h:23 suspicious rcu_dereference_check() usage! [ 68.755264] [ 68.755264] other info that might help us debug this: [ 68.755264] [ 68.758030] [ 68.758030] rcu_scheduler_active = 1, debug_locks = 0 [ 68.760316] 1 lock held by mount/476: [ 68.761896] #0: (&type->s_umount_key#38/1){+.+.+.}, at: [] sget+0x39e/0x670 [ 68.767115] [ 68.767115] stack backtrace: [ 68.769529] Pid: 476, comm: mount Not tainted 3.8.0-0.rc7.git1.1.fc19.x86_64 #1 [ 68.772095] Call Trace: [ 68.772995] [] lockdep_rcu_suspicious+0xe7/0x120 [ 68.775184] [] search_bucket+0x118/0x160 [gfs2] [ 68.777559] [] gfs2_glock_get+0x603/0x7b0 [gfs2] [ 68.780749] [] ? gfs2_glock_get+0x5/0x7b0 [gfs2] [ 68.784173] [] gfs2_glock_nq_num+0x29/0x90 [gfs2] [ 68.786551] [] gfs2_mount+0x869/0xf30 [gfs2] [ 68.788672] [] ? sched_clock_cpu+0xa8/0x100 [ 68.790739] [] ? trace_hardirqs_off+0xd/0x10 [ 68.793042] [] ? local_clock+0x5f/0x70 [ 68.794940] [] ? __mutex_unlock_slowpath+0x80/0x170 [ 68.798236] [] mount_fs+0x39/0x1b0 [ 68.800409] [] ? __alloc_percpu+0x10/0x20 [ 68.803692] [] vfs_kern_mount+0x63/0xf0 [ 68.806773] [] do_mount+0x205/0xa90 [ 68.809669] [] ? might_fault+0x5c/0xb0 [ 68.812717] [] ? strndup_user+0x4b/0xf0 [ 68.816066] [] sys_mount+0x83/0xc0 [ 68.818284] [] system_call_fastpath+0x16/0x1b It would be good to have this silenced for 3.8 but I think there's not long to go. Thanks, Andy >> diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h >> index 31f9d75..2eb8855 100644 >> --- a/include/linux/list_bl.h >> +++ b/include/linux/list_bl.h >> @@ -125,6 +125,11 @@ static inline void hlist_bl_unlock(struct hlist_bl_head *b) >> __bit_spin_unlock(0, (unsigned long *)b); >> } >> >> +static inline bool hlist_bl_is_locked(struct hlist_bl_head *b) >> +{ >> + return bit_spin_is_locked(0, (unsigned long *)b); >> +} >> + >> /** >> * hlist_bl_for_each_entry - iterate over list of given type >> * @tpos: the type * to use as a loop cursor. >> diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h >> index cf1244f..4f216c5 100644 >> --- a/include/linux/rculist_bl.h >> +++ b/include/linux/rculist_bl.h >> @@ -20,7 +20,7 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h, >> static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h) >> { >> return (struct hlist_bl_node *) >> - ((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK); >> + ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK); >> } >> >> /** >> >>