linux-kernel - Re: [PATCH]: In kernel hibernation, suspend to both

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Message-ID: <4FB29F2A.2000607@linux.vnet.ibm.com>
Date:	Tue, 15 May 2012 23:53:38 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Bojan Smojver <bojan@...ursive.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	bp@...en8.de
Subject: Re: [PATCH]: In kernel hibernation, suspend to both

On 05/15/2012 11:12 PM, Rafael J. Wysocki wrote:

> On Tuesday, May 15, 2012, Srivatsa S. Bhat wrote:
>> On 05/15/2012 05:29 AM, Bojan Smojver wrote:
>>
>>> On Mon, 2012-05-14 at 21:47 +1000, Bojan Smojver wrote:
>>>> No. That hangs my box.
>>>>
>>>> This triggers a bug in workqueues code (essentially the same as the
>>>> previous patch, except for sys_sync() not being done):
>>>
>>> Alan/Srivatsa,
>>>
>>> Coming back to the explanation of how this whole thing works, it would
>>> seem that at the point of image writing all devices are fully functional
>>> (not just some, as I mistakenly believed). However, the processes are
>>> supposed to be already frozen, right? Calling suspend_prepare(), which
>>> will essentially try to freeze the processes and kernel threads, seems
>>> like the wrong thing to do.
>>>
>>> Did you guys mean that we should be calling
>>> pm_notifier_call_chain(PM_SUSPEND_PREPARE) only here?
>>>
>>
>>
>> Exactly! And also arrange for the corresponding PM_POST_SUSPEND notification
>> to happen at the end of suspend-to-ram stage...
> 
> Actually, no.  The notifiers are supposed to be called when user space is
> available, otherwise some things will break badly (firmware loading for
> one example IIRC).
> 


Oh, you are right. The notifiers are called before freezing userspace.
Sorry, I had overlooked that.
 
Regards,
Srivatsa S. Bhat

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