Message-ID: <20090424073115.GF24912@elte.hu>
Date:	Fri, 24 Apr 2009 09:31:15 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Greg KH <greg@...ah.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: WARNING: at fs/sysfs/group.c:138 sysfs_remove_group


(more people Cc:-ed - some microcode driver sysdev badness)

* Greg KH <greg@...ah.com> wrote:

> On Thu, Apr 23, 2009 at 01:09:30PM -0700, Andrew Morton wrote:
> > On Fri, 17 Apr 2009 11:13:08 +0200
> > Zdenek Kabelac <zdenek.kabelac@...il.com> wrote:
> > 
> > > Hi
> > > 
> > > 
> > > When I've checked  2.6.30-rc2 kernel and  I've got among other errors
> > > with Wifi message below.
> > > As I've noticed - some people were reporting this problem already earlier:
> > > 
> > > http://www.gossamer-threads.com/lists/linux/kernel/1058276?page=last
> > > 
> > > But for me - it started with 2.6.30-rc kernels.
> > > I've T61, 4GB, C2D, X86_64.
> > > 
> > > 
> > > 
> > > Zdenek
> > > 
> > > 
> > > platform microcode: firmware: requesting intel-ucode/06-0f-0a
> > > platform microcode: firmware: requesting intel-ucode/06-0f-0a
> > 
> > Lots of people are reporting this.  One person reported that each
> > attempt takes 60 seconds, thus delaying boot be several minutes.
> > 
> > > Microcode Update Driver: v2.00 <tigran@...azian.fsnet.co.uk>, Peter Oruba
> > > ------------[ cut here ]------------
> > > WARNING: at fs/sysfs/group.c:138 sysfs_remove_group+0x10b/0x110()
> > > Hardware name: 6464CTO
> > > sysfs group ffffffffa038d900 not found for kobject 'cpu0'
> > > Modules linked in: microcode(-) binfmt_misc dm_mirror dm_region_hash
> > > dm_log dm_mod kvm_intel kvm i915 dr
> > > m i2c_algo_bit uinput btusb bluetooth arc4 ecb cryptomgr aead
> > > pcompress thinkpad_acpi snd_hda_codec_analog crypto_blkcipher
> > > crypto_hash snd_hda_intel cry
> > > pto_algapi snd_hda_codec iwl3945 snd_seq_oss iwlcore
> > > snd_seq_midi_event mac80211 snd_seq rfkill backlight i2c_i801 psmouse
> > > intel_agp snd_seq_device snd_p
> > > cm_oss rtc_cmos rtc_core sr_mod cdrom i2c_core sdhci_pci sdhci
> > > mmc_core serio_raw led_class iTCO_wdt iTCO_vendor_support nvram
> > > cfg80211 snd_mixer_oss e10
> > > 00e rtc_lib snd_pcm snd_timer snd evdev soundcore button ac battery
> > > snd_page_alloc uhci_hcd ohci_hcd ehci_hcd usbcore [last unloaded:
> > > scsi_wait_scan]
> > > Pid: 1983, comm: rmmod Not tainted 2.6.30-rc2-00076-g3ee8da8 #51
> > > Call Trace:
> > >  [<ffffffff802434bf>] warn_slowpath+0xaf/0xf0
> > >  [<ffffffff8039c3dd>] ? kobject_release+0x5d/0xa0
> > >  [<ffffffff80333f7b>] sysfs_remove_group+0x10b/0x110
> > >  [<ffffffffa038b3f8>] mc_sysdev_remove+0x38/0x50 [microcode]
> > >  [<ffffffff8043c08f>] sysdev_driver_unregister+0x5f/0xa0
> > >  [<ffffffffa038bee8>] microcode_exit+0x39/0x65 [microcode]
> > >  [<ffffffff8026e974>] sys_delete_module+0x1b4/0x280
> > >  [<ffffffff8039ff18>] ? __up_write+0xd8/0x150
> > >  [<ffffffff8053e35f>] ? trace_hardirqs_on_thunk+0x3a/0x3c
> > >  [<ffffffff8020c19b>] system_call_fastpath+0x16/0x1b
> > 
> > ugh, where to start?
> > 
> > sysdev_driver_register() calls all the ->add methods and cheerily drops
> > their return codes on the floor.  Consequently
> > sysdev_driver_unregister() will call the ->remove method on objects
> > which were not successfully add()ed.
> 
> Ugh, the sysdev code sucks so badly it's not funny.  It's next on my
> chopping block for cleanups, need to still do some driver core rework
> first though :(
> 
> > mc_sysdev_add() will return an error if microcode_init_cpu() failed but
> > fails to remove its attr_group in that case.  So if
> > sysdev_driver_register()/sysdev_driver_unregister() get fixed,
> > microcode will misbehave.
> > 
> > This patch:
> > 
> > : commit af5c820a3169e81af869c113e18ec7588836cd50
> > : Author:     Rusty Russell <rusty@...tcorp.com.au>
> > : AuthorDate: Wed Mar 11 16:32:36 2009 +1030
> > : Commit:     Ingo Molnar <mingo@...e.hu>
> > : CommitDate: Wed Mar 18 13:50:47 2009 +0100
> > : 
> > :     x86: cpumask: use work_on_cpu in arch/x86/kernel/microcode_core.c
> > : 
> > 
> > attempted to fix things up a bit:
> > 
> > : @@ -379,8 +390,11 @@ static int mc_sysdev_add(struct sys_device *sys_dev)
> > :         if (err)
> > :                 return err;
> > :  
> > : -       microcode_init_cpu(cpu);
> > : -       return 0;
> > : +       err = microcode_init_cpu(cpu);
> > : +       if (err)
> > : +               sysfs_remove_group(&sys_dev->kobj, &mc_attr_group);
> > : +
> > : +       return err;
> > :  }
> > :  
> > :  static int mc_sysdev_remove(struct sys_device *sys_dev)
> > 
> > But it seems that the sysfs_remove_group() later got removed again.
> 
> So, this is a microcode specific issue?

Hm, it really doesnt do anything fancy. I've Cc:-ed a few more 
folks. There's a patch to try in this thread on lkml:

[PATCH] x86 microcode: work_on_cpu and cleanup of the synchronization logic

(note, try the v2 patch in that discussion. There will be a v3 patch 
too there.)

But that patch does not specifically address any sysdev related 
buglet.

	Ingo
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