Message-ID: <4F140872.3090409@linux.vnet.ibm.com>
Date:	Mon, 16 Jan 2012 16:52:26 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Sergei Trofimovich <slyich@...il.com>
CC:	linux-kernel@...r.kernel.org, Kay Sievers <kay.sievers@...y.org>,
	Linux PM mailing list <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Tony Luck <tony.luck@...el.com>,
	"mingo@...e.hu" <mingo@...e.hu>, Borislav Petkov <bp@...64.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	prasad@...ux.vnet.ibm.com
Subject: Re: 3.2.0-07927-gc49c41a: s2ram: Device 'machinecheck1' does not
 have a release() function, it is broken and must be fixed

On 01/16/2012 03:48 PM, Sergei Trofimovich wrote:

> With 3.2.0-rc0 I was not able to s2ram twice in a row. Bisected down to
> 
>   commit 8a25a2fd126c621f44f3aeaef80d51f00fc11639
>   Author: Kay Sievers <kay.sievers@...y.org>
>   Date:   Wed Dec 21 14:29:42 2011 -0800
> 
>       cpu: convert 'cpu' and 'machinecheck' sysdev_class to a regular subsystem
> 
> it was fixed recently by commit
> 
>   commit a3301b751b19f0efbafddc4034f8e7ce6bf3007b
>   Author: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>   Date:   Sat Jan 14 08:11:31 2012 +0530
> 
>     x86/mce: Fix CPU hotplug and suspend regression related to MCE
> 
> alas the warning pop ups (3.2.0-07927-gc49c41a).
> 
> command for suspend:
>     sudo sh -c "echo mem > /sys/power/state"
> 
> [ 7915.604188] ------------[ cut here ]------------
> [ 7915.604203] WARNING: at drivers/base/core.c:194 device_release+0x85/0x90()
> [ 7915.604209] Hardware name: HP Compaq 2510p Notebook PC
> [ 7915.604214] Device 'machinecheck1' does not have a release() function, it is broken and must be fixed.
> [ 7915.604219] Modules linked in: snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss
>  ext2 loop kvm_intel kvm fuse scsi_wait_scan usb_storage tun snd_hda_codec_analog snd_hda_intel snd_hda_codec snd_hwdep snd_pcm
>  snd_timer iwl4965 iwlegacy snd mac80211 cfg80211 yenta_socket soundcore pcmcia_core pcmcia_rsrc rfkill i915 sdhci_pci drm_kms_
> helper sdhci mmc_core drm e1000e snd_page_alloc i2c_algo_bit
> [ 7915.604293] Pid: 30171, comm: sh Not tainted 3.2.0-07927-gc49c41a #190
> [ 7915.604298] Call Trace:
> [ 7915.604311]  [<ffffffff81038f9a>] warn_slowpath_common+0x7a/0xb0
> [ 7915.604320]  [<ffffffff81039071>] warn_slowpath_fmt+0x41/0x50
> [ 7915.604331]  [<ffffffff81060781>] ? get_parent_ip+0x11/0x50
> [ 7915.604338]  [<ffffffff8130a3d5>] device_release+0x85/0x90
> [ 7915.604348]  [<ffffffff8125483d>] kobject_release+0x8d/0x1d0
> [ 7915.604356]  [<ffffffff812546dc>] kobject_put+0x2c/0x60
> [ 7915.604364]  [<ffffffff8130a122>] put_device+0x12/0x20
> [ 7915.604371]  [<ffffffff8130b235>] device_unregister+0x25/0x60
> [ 7915.604383]  [<ffffffff81450485>] mce_cpu_callback+0xe2/0x18a
> [ 7915.604392]  [<ffffffff8105b4bc>] notifier_call_chain+0x4c/0x70
> [ 7915.604400]  [<ffffffff8105b569>] __raw_notifier_call_chain+0x9/0x10
> [ 7915.604408]  [<ffffffff8103ab1b>] __cpu_notify+0x1b/0x30
> [ 7915.604416]  [<ffffffff8103ab40>] cpu_notify+0x10/0x20
> [ 7915.604423]  [<ffffffff8103ab59>] cpu_notify_nofail+0x9/0x20
> [ 7915.604433]  [<ffffffff8144345b>] _cpu_down+0x13b/0x250
> [ 7915.604441]  [<ffffffff8145536c>] ? printk+0x3c/0x40
> [ 7915.604450]  [<ffffffff8103ad76>] disable_nonboot_cpus+0x86/0x120
> [ 7915.604460]  [<ffffffff81083598>] suspend_devices_and_enter+0x148/0x240
> [ 7915.604469]  [<ffffffff810837e9>] enter_state+0x159/0x180
> [ 7915.604477]  [<ffffffff81082606>] state_store+0xc6/0x140
> [ 7915.604485]  [<ffffffff81254567>] kobj_attr_store+0x17/0x20
> [ 7915.604494]  [<ffffffff81142ce4>] sysfs_write_file+0xf4/0x170
> [ 7915.604504]  [<ffffffff810e15e6>] vfs_write+0xc6/0x180
> [ 7915.604512]  [<ffffffff810e18fc>] sys_write+0x4c/0x90
> [ 7915.604521]  [<ffffffff81459122>] system_call_fastpath+0x16/0x1b
> [ 7915.604528] ---[ end trace a06cd82fe48c1076 ]---
> 


Hi Sergei,

As I noted in the mail in which I posted that patch
(http://thread.gmane.org/gmane.linux.kernel/1237745/focus=1239134),
my patch just fixes the suspend issue. It doesn't attempt to fix the
"machinecheck not having a release() function" warning. And as mentioned
in the preceding discussion in the same thread,
(http://thread.gmane.org/gmane.linux.kernel/1237745/focus=1239052)
this warning is not a problem for suspend to work.

Of course, we have to get rid of this warning and one easy and trivial
way to get rid of this would be to add a dummy release() function for
MCE, since technically there is nothing to be released, since we use
per-cpu allocations of struct device.

But the only reason I haven't really jumped into writing such a patch
is that I would prefer to get the semantics right - adding a dummy
function is IMO something like working around the rules of the driver-core
framework just to silence the warning. Hence I feel we should resort
to it _only_ if there is nothing better we can do about this.

Just to re-instate, an end-user need not really worry about this warning
too much since this was there before (at a different place, and hidden)
when things were working fine... Hence it would be worthwhile to fix
this warning "correctly" if possible, than just do a quick and dirty
"silence the warning" kind of workaround. 

Regards,
Srivatsa S. Bhat
IBM Linux Technology Center

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