Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753930AbZFRFqn (ORCPT ); Thu, 18 Jun 2009 01:46:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753150AbZFRFqf (ORCPT ); Thu, 18 Jun 2009 01:46:35 -0400 Received: from mail-ew0-f210.google.com ([209.85.219.210]:48537 "EHLO mail-ew0-f210.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752382AbZFRFqc convert rfc822-to-8bit (ORCPT ); Thu, 18 Jun 2009 01:46:32 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=ZiGMWL1tR5MnGy7ZroLkQCGSR/IycWxqiG5z6V4fvyEFasti/Z8e064oPZyL4rYTzZ Uq7HEE8RsrKtPaF9GNhz/9eH5cL56BXIN1bJZ6NxvxIiFrn52v+1Zztlc1uW98D8o/Jv +q5wLO7EGrVOeHV6DNMC+juvAEYOA9h/vjA9I= MIME-Version: 1.0 In-Reply-To: <20090617003925.GA3900@linux-os.sc.intel.com> References: <84144f020906070621r1f480eaeief026d23662df380@mail.gmail.com> <1244447366.13471.4.camel@penberg-laptop> <20090608124844.GA17588@Krystal> <20090608143220.GC2516@redhat.com> <1244727561.5350.32.camel@odie.local> <20090611152329.GB28099@Krystal> <20090617003925.GA3900@linux-os.sc.intel.com> Date: Thu, 18 Jun 2009 13:46:33 +0800 Message-ID: Subject: Re: [Bug #13475] suspend/hibernate lockdep warning From: Dave Young To: "Pallipadi, Venkatesh" Cc: Mathieu Desnoyers , =?UTF-8?Q?Simon_Holm_Th=C3=B8gersen?= , Dave Jones , Pekka Enberg , "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , "cpufreq@vger.kernel.org" , Rusty Russell , "trenn@suse.de" , "sven.wegener@stealer.net" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 14673 Lines: 319 On Wed, Jun 17, 2009 at 8:39 AM, Pallipadi, Venkatesh wrote: > On Thu, Jun 11, 2009 at 08:23:29AM -0700, Mathieu Desnoyers wrote: >> * Simon Holm Thøgersen (odie@cs.aau.dk) wrote: >> > man, 08 06 2009 kl. 10:32 -0400, skrev Dave Jones: >> > > On Mon, Jun 08, 2009 at 08:48:45AM -0400, Mathieu Desnoyers wrote: >> > > >> > >  > > > >> Bug-Entry       : http://bugzilla.kernel.org/show_bug.cgi?id=13475 >> > >  > > > >> Subject         : suspend/hibernate lockdep warning >> > >  > > > >> References      : http://marc.info/?l=linux-kernel&m=124393723321241&w=4 >> > >  > > > >> > >  > > > I suspect the following commit, after revert this patch I test 5 times >> > >  > > > without lockdep warnings. >> > >  > > > >> > >  > > > commit b14893a62c73af0eca414cfed505b8c09efc613c >> > >  > > > Author: Mathieu Desnoyers >> > >  > > > Date:   Sun May 17 10:30:45 2009 -0400 >> > >  > > > >> > >  > > >    [CPUFREQ] fix timer teardown in ondemand governor >> > >  > > >> > >  > > The patch is probably not at fault here. I suspect it's some latent bug >> > >  > > that simply got exposed by the change to cancel_delayed_work_sync(). In >> > >  > > any case, Mathieu, can you take a look at this please? >> > >  > >> > >  > Yes, it's been looked at and discussed on the cpufreq ML. The short >> > >  > answer is that they plan to re-engineer cpufreq and remove the policy >> > >  > rwlock taken around almost every operations at the cpufreq level. >> > >  > >> > >  > The short-term solution, which is recognised as ugly, would be do to the >> > >  > following before doing the cancel_delayed_work_sync() : >> > >  > >> > >  > unlock policy rwlock write lock >> > >  > >> > >  > lock policy rwlock write lock >> > >  > >> > >  > It basically works because this rwlock is unneeded for teardown, hence >> > >  > the future re-work planned. >> > >  > >> > >  > I'm sorry I cannot prepare a patch current... I've got quite a few pages >> > >  > of Ph.D. thesis due for the beginning of July. >> > > >> > > I'm kinda scared to touch this code at all for .30 due to the number of >> > > unexpected gotchas we seem to run into every time we touch something >> > > locking related.  So I'm inclined to just live with the lockdep warning >> > > for .30, and see how the real fixes look for .31, and push them back >> > > as -stable updates if they work out. >> > >> > Unfortunately I don't think it is just theoretical, I've actually hit >> > the following (that haven't got anything to do with suspend/hibernate) >> > >> > INFO: task cpufreqd:4676 blocked for more than 120 seconds. >> >  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> >  cpufreqd      D eee2ac60     0  4676      1 >> >   ee01bd68 00000086 eee2aad0 eee2ac60 00000533 eee2aad0 eee2ac60 0002b16f >> >   00000000 eee2ac60 7fffffff 7fffffff eee2ac60 7fffffff 7fffffff 00000000 >> >   ee01bd70 c03117ee ee01bdbc c0311c0c eee2aad0 eecf6900 eee2aad0 eecf6900 >> >  Call Trace: >> >   [] schedule+0x12/0x24 >> >   [] schedule_timeout+0x17/0x170 >> >   [] ? __wake_up+0x2b/0x51 >> >   [] wait_for_common+0xc4/0x135 >> >   [] ? default_wake_function+0x0/0xd >> >   [] wait_for_completion+0x12/0x14 >> >   [] __cancel_work_timer+0xfe/0x129 >> >   [] ? wq_barrier_func+0x0/0xd >> >   [] cancel_delayed_work_sync+0xb/0xd >> >   [] cpufreq_governor_dbs+0x22e/0x291 [cpufreq_ondemand] >> >   [] __cpufreq_governor+0x65/0x9d >> >   [] __cpufreq_set_policy+0xd1/0x11f >> >   [] store_scaling_governor+0x18a/0x1b2 >> >   [] ? handle_update+0x0/0xd >> >   [] ? store_scaling_governor+0x0/0x1b2 >> >   [] store+0x48/0x61 >> >   [] sysfs_write_file+0xb4/0xdf >> >   [] ? sysfs_write_file+0x0/0xdf >> >   [] vfs_write+0x8a/0x104 >> >   [] sys_write+0x3b/0x60 >> >   [] sysenter_do_call+0x12/0x2c >> >  INFO: task kondemand/0:4956 blocked for more than 120 seconds. >> >  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> >  kondemand/0   D 00000533     0  4956      2 >> >   ee1d9efc 00000046 c011815f 00000533 071148de ee1e0080 ee1e0210 00000000 >> >   c03ff478 9189e633 00000082 c03ff478 ee1e0210 c04159f4 c04159f0 00000000 >> >   ee1d9f04 c03117ee ee1d9f28 c0313104 ee1d9f30 c04159f4 ee1e0080 c01183be >> >  Call Trace: >> >   [] ? update_curr+0x6c/0x14b >> >   [] schedule+0x12/0x24 >> >   [] rwsem_down_failed_common+0x150/0x16e >> >   [] ? dequeue_task_fair+0x51/0x56 >> >   [] rwsem_down_write_failed+0x1b/0x23 >> >   [] call_rwsem_down_write_failed+0x6/0x8 >> >   [] ? down_write+0x14/0x16 >> >   [] lock_policy_rwsem_write+0x1d/0x33 >> >   [] do_dbs_timer+0x45/0x266 [cpufreq_ondemand] >> >   [] worker_thread+0x165/0x212 >> >   [] ? do_dbs_timer+0x0/0x266 [cpufreq_ondemand] >> >   [] ? autoremove_wake_function+0x0/0x33 >> >   [] ? worker_thread+0x0/0x212 >> >   [] kthread+0x42/0x67 >> >   [] ? kthread+0x0/0x67 >> >   [] kernel_thread_helper+0x7/0x10 >> > >> > I've only seen it once in 5 boots and CONFIG_PROVELOCKING does not give any >> > warnings about this, though it does yell when switching governor as reported >> > by others in bug #13493. >> > >> > Let's hope Mathieu nails it, though I know he's busy with his thesis. >> > >> >> Thanks for the lockdep reports, >> >> I'm currently looking into it, and it's not pretty. Basically we have : >> >> A >>   B >> (means B nested in A) >> >> work >>   read rwlock policy >> >> dbs_mutex >>   work >>     read rwlock policy >> >> write rwlock policy >>   dbs_mutex >> >> So the added dbs_mutex <- work <- rwlock policy dependency (for proper >> teardown) is firing the reverse dependency between policy rwlock and >> dbs_mutex. >> >> The real way to fix this is to do not take the rwlock policy around >> non-policy-related actions, like governor START/STOP doing worker >> creation/teardown. >> >> One simple short-term solution would be to take a mutex outside of the >> policy rwlock write lock in cpufreq.c. This mutex would be the >> equivalent of dbs_mutex "lifted" outside of the rwlock write lock. For >> teardown, we only need to hold this mutex, not the rwlock write lock. >> Then we can remove the dbs_mutex from the governors. >> >> But looking at cpufreq.c's cpufreq_add_dev() is very much like kicking a >> wasp nest: a lot of error paths are not handled properly, and I fear >> someone will have to go through the code, fix the currently incorrect >> code paths, and then add the lifted mutex. >> >> I currently have no time for implementation due to my thesis, but I'll >> be happy to review a patch. >> > > How about below patch on top of Mathieu's patch here > http://marc.info/?l=linux-kernel&m=124448150529838&w=2 > > [PATCH] cpufreq: Eliminate lockdep issue with dbs_mutex and policy_rwsem > > This removes the unneeded dependency of > write rwlock policy >  dbs_mutex > > dbs_mutex does not have anything to do with timer_init and timer_exit. It > is just to protect dbs tunables in sysfs cpufreq/ondemand and is not > needed to be held during timer init, exit as well as during governor limit > changes. > > Signed-off-by: Venkatesh Pallipadi > --- >  drivers/cpufreq/cpufreq_ondemand.c |    8 +++----- >  1 files changed, 3 insertions(+), 5 deletions(-) latest linux-2.6 git + this patch, hibernate test result: [ 221.956815] [ 221.956817] ======================================================= [ 221.957017] [ INFO: possible circular locking dependency detected ] [ 221.957173] 2.6.30-06692-g3fe0344-dirty #77 [ 221.957276] ------------------------------------------------------- [ 221.957431] 94cpufreq/1914 is trying to acquire lock: [ 221.957561] (&(&dbs_info->work)->work){+.+...}, at: [] __cancel_work_timer+0x8c/0x18c [ 221.958034] [ 221.958036] but task is already holding lock: [ 221.958336] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [] lock_policy_rwsem_write+0x33/0x5b [ 221.958850] [ 221.958852] which lock already depends on the new lock. [ 221.958855] [ 221.959258] [ 221.959260] the existing dependency chain (in reverse order) is: [ 221.959625] [ 221.959627] -> #1 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}: [ 221.959994] [] __lock_acquire+0x91e/0xaa9 [ 221.959994] [] lock_acquire+0x9b/0xbe [ 221.959994] [] down_write+0x2f/0x4b [ 221.959994] [] lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [] do_dbs_timer+0x45/0x23b [ 221.959994] [] worker_thread+0x170/0x23c [ 221.959994] [] kthread+0x45/0x6e [ 221.959994] [] kernel_thread_helper+0x7/0x10 [ 221.959994] [] 0xffffffff [ 221.959994] [ 221.959994] -> #0 (&(&dbs_info->work)->work){+.+...}: [ 221.959994] [] __lock_acquire+0x82e/0xaa9 [ 221.959994] [] lock_acquire+0x9b/0xbe [ 221.959994] [] __cancel_work_timer+0xb7/0x18c [ 221.959994] [] cancel_delayed_work_sync+0xb/0xd [ 221.959994] [] cpufreq_governor_dbs+0x1f7/0x263 [ 221.959994] [] __cpufreq_governor+0x66/0x9d [ 221.959994] [] __cpufreq_set_policy+0x13f/0x1c3 [ 221.959994] [] store_scaling_governor+0x159/0x188 [ 221.959994] [] store+0x42/0x5b [ 221.959994] [] sysfs_write_file+0xb8/0xe3 [ 221.959994] [] vfs_write+0x82/0xdc [ 221.959994] [] sys_write+0x3b/0x5d [ 221.959994] [] syscall_call+0x7/0xb [ 221.959994] [] 0xffffffff [ 221.959994] [ 221.959994] other info that might help us debug this: [ 221.959994] [ 221.959994] 2 locks held by 94cpufreq/1914: [ 221.959994] #0: (&buffer->mutex){+.+.+.}, at: [] sysfs_write_file+0x25/0xe3 [ 221.959994] #1: (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [] lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [ 221.959994] stack backtrace: [ 221.959994] Pid: 1914, comm: 94cpufreq Not tainted 2.6.30-06692-g3fe0344-dirty #77 [ 221.959994] Call Trace: [ 221.959994] [] print_circular_bug_tail+0x5d/0x68 [ 221.959994] [] __lock_acquire+0x82e/0xaa9 [ 221.959994] [] ? mark_lock+0x1e/0x1c7 [ 221.959994] [] lock_acquire+0x9b/0xbe [ 221.959994] [] ? __cancel_work_timer+0x8c/0x18c [ 221.959994] [] __cancel_work_timer+0xb7/0x18c [ 221.959994] [] ? __cancel_work_timer+0x8c/0x18c [ 221.959994] [] ? mark_held_locks+0x43/0x5b [ 221.959994] [] ? __mutex_unlock_slowpath+0xf1/0x101 [ 221.959994] [] ? trace_hardirqs_on+0xb/0xd [ 221.959994] [] cancel_delayed_work_sync+0xb/0xd [ 221.959994] [] cpufreq_governor_dbs+0x1f7/0x263 [ 221.959994] [] ? up_read+0x16/0x29 [ 221.959994] [] __cpufreq_governor+0x66/0x9d [ 221.959994] [] __cpufreq_set_policy+0x13f/0x1c3 [ 221.959994] [] ? store_scaling_governor+0x0/0x188 [ 221.959994] [] store_scaling_governor+0x159/0x188 [ 221.959994] [] ? handle_update+0x0/0x28 [ 221.959994] [] ? lock_policy_rwsem_write+0x33/0x5b [ 221.959994] [] ? store_scaling_governor+0x0/0x188 [ 221.959994] [] store+0x42/0x5b [ 221.959994] [] sysfs_write_file+0xb8/0xe3 [ 221.959994] [] vfs_write+0x82/0xdc [ 221.959994] [] ? sysfs_write_file+0x0/0xe3 [ 221.959994] [] sys_write+0x3b/0x5d [ 221.959994] [] syscall_call+0x7/0xb [ 222.336101] PM: Marking nosave pages: 000000000009f000 - 0000000000100000 [ 222.340205] PM: Basic memory bitmaps created [ 222.344226] PM: Syncing filesystems ... done. > > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c > index e741c33..1c94ff5 100644 > --- a/drivers/cpufreq/cpufreq_ondemand.c > +++ b/drivers/cpufreq/cpufreq_ondemand.c > @@ -352,8 +352,8 @@ static ssize_t store_powersave_bias(struct cpufreq_policy *unused, > >        mutex_lock(&dbs_mutex); >        dbs_tuners_ins.powersave_bias = input; > -       ondemand_powersave_bias_init(); >        mutex_unlock(&dbs_mutex); > +       ondemand_powersave_bias_init(); > >        return count; >  } > @@ -626,14 +626,14 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, > >                        dbs_tuners_ins.sampling_rate = def_sampling_rate; >                } > +               mutex_unlock(&dbs_mutex); >                dbs_timer_init(this_dbs_info); > > -               mutex_unlock(&dbs_mutex); >                break; > >        case CPUFREQ_GOV_STOP: > -               mutex_lock(&dbs_mutex); >                dbs_timer_exit(this_dbs_info); > +               mutex_lock(&dbs_mutex); >                sysfs_remove_group(&policy->kobj, &dbs_attr_group); >                dbs_enable--; >                mutex_unlock(&dbs_mutex); > @@ -641,14 +641,12 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, >                break; > >        case CPUFREQ_GOV_LIMITS: > -               mutex_lock(&dbs_mutex); >                if (policy->max < this_dbs_info->cur_policy->cur) >                        __cpufreq_driver_target(this_dbs_info->cur_policy, >                                policy->max, CPUFREQ_RELATION_H); >                else if (policy->min > this_dbs_info->cur_policy->cur) >                        __cpufreq_driver_target(this_dbs_info->cur_policy, >                                policy->min, CPUFREQ_RELATION_L); > -               mutex_unlock(&dbs_mutex); >                break; >        } >        return 0; > -- > 1.6.0.6 > > -- Regards dave -- 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/