[xfs-masters] Re: freeze vs freezer

[Nigel Cunningham <nigel@xxxxxxxxxxxxxxxxxx>]

Hi.

Pavel Machek wrote:
> Hi!
> 
>>>>>> So how do you handle threads that are blocked on I/O or a lock  
>>>>>> during the system freeze process, then?
>>>>> We wait until they can continue.
>>>> So if I have a process blocked on an unavilable NFS mount, I can't
>>>> suspend?
>>> That's correct, you can't.
>>>
>>> [And I know what you're going to say. ;-)]
>> Why exactly does suspend/hibernation depend on "TASK_INTERRUPTIBLE"  
>> instead of a zero preempt_count()?  Really what we should do is just  
>> iterate over all of the actual physical devices and tell each one  
>> "Block new IO requests preemptably, finish pending DMA, put the  
>> hardware in low-power mode, and prepare for suspend/hibernate".  As  
>> long as each driver knows how to do those simple things we can have  
>> an entirely consistent kernel image for both suspend and for  
>> hibernation.
> 
> "each driver" means this is a lot of work. But yes, that is probably
> way to go, and patch would be welcome.

Yes, that does work. It's what I've done in my (preliminary) support for
fuse.

Regards,

Nigel