linux-kernel - Re: SwSusp to disk doesn't work

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Date:	Sun, 11 Mar 2007 22:57:01 +0100
From:	Thomas Meyer <thomas@...3r.de>
To:	tglx@...utronix.de
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, Milan Broz <mbroz@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Pavel Machek <pavel@....cz>
Subject: Re: SwSusp to disk doesn't work - Try 2

Thomas Gleixner schrieb:
> On Sun, 2007-03-11 at 22:09 +0100, Rafael J. Wysocki wrote:
>   
>>>>>>>>     update_sched_domains
>>>>>>>>      detach_destroy_domains
>>>>>>>>        [waits here] --> synchronize_sched (==synchronize_rcu)
>>>>>>>>         
>>>>>>>>                 
>>>>>>> Well, I think the call to wait_for_completion() does not return, probably
>>>>>>> because the task supposed to complete the completion is frozen at this
>>>>>>> point.  Can you please try to confirm that it gets stuck on
>>>>>>> wait_for_completion() in synchronize_rcu()?
>>>>>>>       
>>>>>>>               
>>>>>> Yes, it's in wait_for_completion() in synchronize_rcu().
>>>>>> As noted in some previous mail, it will wake up after
>>>>>> event - key press etc.
>>>>>>
>>>>>> Patch in http://lkml.org/lkml/2007/3/7/255 solves different problem.
>>>>>> I added it to my quilt and applied anyway -> no change.
>>>>>>     
>>>>>>             
>>>>> Does the problem go away if NO_HZ is unset?
>>>>>   
>>>>>           
>>>> i tried to boot with nohz=off, but the problem did persist.
>>>>         
>>> Hmmmm, both variants (nohz=off or recompiled kernel without NO_HZ) works for me.
>>>       
>> Definitely something strange is going on here.
>>
>> I think we need an advice from someone who knows the RCU internals.
>>     
>
> RCU synchronization depends on the timer interrupt. Which kernel version
> are you guys talking about ?
>
> 	tglx
>   

I talk about be521466feb3bb1cd89de82a2b1d080e9ebd3cb6 (2.6.21-rc3+).

The worst config is with nohz and without hrtimers: the kernel even 
doesn't come back after pressing the power key.

But i stay with without nohz and without hrtimers for now, because here 
the suspend to disk works.

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