linux-kernel - Re: [PATCH] drivers/base/power: reset transition_started at dpm_resume

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Date:	Wed, 19 Aug 2009 22:58:58 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Xiaotian Feng <dfeng@...hat.com>, gregkh@...e.de, pavel@....cz,
	len.brown@...el.com, damm@...l.co.jp,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/base/power: reset transition_started at dpm_resume_noirq

On Wednesday 19 August 2009, Alan Stern wrote:
> On Wed, 19 Aug 2009, Rafael J. Wysocki wrote:
> 
> > On Monday 17 August 2009, Xiaotian Feng wrote:
> > > transition_started should be set once the preparation of devices for
> > > a PM has started, reset before starting to resume devices. When resuming
> > > devices, kernel calls dpm_resume_noirq then dpm_resume_end(dpm_resume).
> > > Thus we should reset transition_started at dpm_resume_noirq.
> > > 
> > > This patch fixes acpi warning when resuming from suspend/hibernate:
> > > 
> > > ACPI: \_SB_.PCI0.IDE1.PRI1.MAS1 - docking
> > > ------------[ cut here ]------------
> > > WARNING: at drivers/base/power/main.c:87 device_pm_add+0x8b/0xcc()
> > > Hardware name: OptiPlex 760
> > > Device: acpi
> > > Parentless device registered during a PM transaction
> > > Modules linked in: fuse sco bridge stp llc bnep l2cap bluetooth sunrpc ip6t_REJECT nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 dm_multipath uinput snd_hda_codec_analog radeon ppdev parport_pc snd_hda_intel ttm snd_hda_codec serio_raw snd_hwdep iTCO_wdt drm i2c_i801 parport iTCO_vendor_support pcspkr snd_pcm snd_timer i2c_algo_bit i2c_core snd dcdbas wmi e1000e soundcore snd_page_alloc ata_generic pata_acpi [last unloaded: speedstep_lib]
> > > Pid: 33, comm: kacpi_hotplug Not tainted 2.6.31-rc5 #51
> > > Call Trace:
> > >  [<ffffffff8104ece1>] warn_slowpath_common+0x7c/0x94
> > >  [<ffffffff8104ed50>] warn_slowpath_fmt+0x41/0x43
> > >  [<ffffffff812ae827>] device_pm_add+0x8b/0xcc
> > >  [<ffffffff812a820b>] device_add+0x36f/0x519
> > >  [<ffffffff812a83d3>] device_register+0x1e/0x22
> > >  [<ffffffff81245c86>] acpi_add_single_object+0xb48/0xd68
> > >  [<ffffffff810750d6>] ? trace_hardirqs_on_caller+0x1f/0x159
> > >  [<ffffffff8107521d>] ? trace_hardirqs_on+0xd/0xf
> > >  [<ffffffff812461cb>] acpi_bus_add+0x2a/0x40
> > >  [<ffffffff81244128>] ? acpi_bus_get_device+0x47/0x66
> > >  [<ffffffff81247c52>] hotplug_dock_devices+0x109/0x133
> > >  [<ffffffff812423b1>] ? acpi_os_execute_hp_deferred+0x0/0x43
> > >  [<ffffffff81248013>] acpi_dock_deferred_cb+0xbf/0x192
> > >  [<ffffffff812423e7>] acpi_os_execute_hp_deferred+0x36/0x43
> > >  [<ffffffff8106099a>] worker_thread+0x215/0x31d
> > >  [<ffffffff81060945>] ? worker_thread+0x1c0/0x31d
> > >  [<ffffffff81415f34>] ? thread_return+0x3e/0xaf
> > >  [<ffffffff810739bb>] ? lock_release_holdtime+0x2c/0x11d
> > >  [<ffffffff8106549e>] ? autoremove_wake_function+0x0/0x39
> > >  [<ffffffff81060785>] ? worker_thread+0x0/0x31d
> > >  [<ffffffff8106513c>] kthread+0x8a/0x92
> > >  [<ffffffff81012d4a>] child_rip+0xa/0x20
> > >  [<ffffffff810126d0>] ? restore_args+0x0/0x30
> > >  [<ffffffff810650b2>] ? kthread+0x0/0x92
> > >  [<ffffffff81012d40>] ? child_rip+0x0/0x20
> > > ---[ end trace 6f4892372e7d9f1a ]---
> > > 
> > > Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
> > 
> > OK, we can do this IMO.
> > 
> > Alan, what do you think?
> 
> I suppose so.  The difference between dpm_resume() and 
> dpm_resume_noirq() is minimal.
> 
> But at the same time, I wonder if this isn't really a bug in ACPI.  
> Why does it want to register a new top-level device during the 
> resume_noirq phase?
> 
> The stack trace indicates that the registration occurred from within a
> workqueue.  Maybe it should be moved to a freezable workqueue; that
> would prevent it from happening too early.

This looks like the box was put into a docking station while suspended or
something like this, which would indicate that the action was legitimate.

Anyway, I don't think that's anything the core has to care about. :-)

Thanks,
Rafael
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