[Devel] Re: [RFC][PATCH 0/4] Container Freezer

[Cedric Le Goater]

Dave Hansen wrote:
> On Wed, 2007-06-20 at 18:22 +0200, Cedric Le Goater wrote:
>> I would be in favor of adding a new c/r signal like other operating systems 
>> have done today and in the past. This is something to discuss. 
> 
> There was some talk of doing a new signal for CPU hotplug.  But, that
> was shot down because it really requires library changes to work right.
> But, would this signal be completely kernel handled?  What good is 
> having a signal if userspace *isn't* going to handle it ever?

There are 2 reasons for such a signal. 

The first is to be able to freeze a group of tasks before checkpointing 
it. the swsusp freezer does that already, with a stealth signal by 
faking it. 

The second is to be able to run some code in the context of the current 
task. There's plenty of simple ways to get/set process and kernel states 
through syscalls. Why not use them ? Of course, we cannot do everything 
in user and, whenever needed ,we would use a kernel helper. memory is
one requiring a big helper (swap).

It would also require to have a user space handler in some lib. 

I'd like to address that topic at the C/R bof.

Thanks,

C.
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