linux-kernel - Re: INFO: possible circular locking dependency

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Message-ID: <c4e36d110908260712u3aa0e27ft869049aa310a7386@mail.gmail.com>
Date:	Wed, 26 Aug 2009 16:12:19 +0200
From:	Zdenek Kabelac <zdenek.kabelac@...il.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	len.brown@...el.com, linux-acpi@...r.kernel.org,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Zhang Rui <rui.zhang@...el.com>, Paul Martin <pm@...ian.org>,
	Vojtech Gondzala <vojtech.gondzala@...il.com>
Subject: Re: INFO: possible circular locking dependency - kacpid 
	acpi_os_wait_events_complete

2009/8/25 Bjorn Helgaas <bjorn.helgaas@...com>:
> On Tuesday 25 August 2009 02:33:30 pm you wrote:
>> 2009/8/25 Bjorn Helgaas <bjorn.helgaas@...com>:
>> > On Tuesday 25 August 2009 02:10:58 am Zdenek Kabelac wrote:
>> >> Now with 2.6.31-rc7 (3edf2fb9d80a46d6c32ba12547a42419845b4b76)
>> >>  I'm getting this  INFO trace - also I've noticed complete reset during resume
>> >> which could be eventually related to this
>> > Do you have any evidence that points to thinkpad_acpi?  I looked
>> > at the recent changes there, and I don't see anything obviously
>> > related to kacpid or deferred work.
>> >
>>
>> Well I've never seen this INFO trace before - also I'm not sure I
>> could reliable retest it - might be coincidence of suspend out of port
>> replicator and resume while being attached on it - however I do this
>> relatively often and I start to see this after I' started to use -rc7
>> kernel.
>>
>> My guess is purely based on the fact that commit touching functions
>> from INFO trace was recently merged to main tree.
>>
>> If there will be some time I could try to make few tests for suspend
>> resume - but I hope the trace would be enough for analysis.
>

Well definitelly I do not have a reliable test case to
deterministically trigger this INFO trace, but I think from the trace
it looks like  the acpi_os_wait_events_complete calls flush_workqueue
which again calls acpi_os_execute_hp_deferred which again tries to
invoke flush_workqueue - so is that correct ?

(__acpi_os_execute looks somewhat cryptic in selection what would be called)

This is the stack traceback cut from my first post:

 [<ffffffff81064df0>] ? flush_workqueue+0x0/0xc0
 [<ffffffff81261532>] ? acpi_os_execute_hp_deferred+0x0/0x43
 [<ffffffff81064e4f>] flush_workqueue+0x5f/0xc0
 [<ffffffff81064df0>] ? flush_workqueue+0x0/0xc0
 [<ffffffff81261524>] acpi_os_wait_events_complete+0x15/0x23
 [<ffffffff81261561>] acpi_os_execute_hp_deferred+0x2f/0x43
 [<ffffffff810651d4>] worker_thread+0x1e4/0x3f0

So it looks like this issue is releated to commit:
c02256be79a1a3557332ac51e653d574a2a7d2b5

Hopefully the author would be able to fix this ?

Zdenek
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