linux-kernel - Re: [PATCH] driver core: Ensure proper suspend/resume ordering

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Date:	Wed, 16 Sep 2015 16:38:32 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alan Stern <stern@...land.harvard.edu>
CC:	Thierry Reding <thierry.reding@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] driver core: Ensure proper suspend/resume ordering

On 09/16/2015 04:28 AM, Rafael J. Wysocki wrote:
> On Tuesday, September 15, 2015 03:18:19 PM Alan Stern wrote:
>> On Tue, 15 Sep 2015, Thierry Reding wrote:
>>
>>>> There are a few things to watch out for.  Since the dpm_list gets
>>>> modified during system sleep transitions, we would have to make sure
>>>> that nothing gets probed during those times.  In principle, that's what
>>>> the "prepare" stage is meant for, but there's still a race.  As long as
>>>> no other kernel thread (such as the deferred probing mechanism) tries
>>>> to probe a device once everything has been frozen, we should be okay.
>>>> But if not, there will be trouble -- after the ->prepare callback runs,
>>>> the device is no longer on the dpm_list and so we don't want this patch
>>>> to put it back on that list.
>>>
>>> Perhaps moving to the end of the list needs to be a little smarter. That
>>> is it could check whether the device has been prepared for suspension or
>>> not and only move when it hasn't?
>>
>> Maybe.  But doesn't that mean it won't solve your problem completely?
>>
>>> Then again, shouldn't the core even prohibit new probes once the suspend
>>> has been triggered? Sounds like asking for a lot of trouble if it didn't
>>> ...
>>
>> The core prohibits new devices from being registered.  It does not
>> prohibit probes of existing devices, because they currently do not
>> affect the dpm_list.

Seems I missed smth, but I can't find the place in Kernel that prohibits
creation of new devices during suspend.

Could someone point me on, please?




-- 
regards,
-grygorii
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