FreeBSD disk hibernation - Was: Resuming from a crashdump

[João Carlos Mendes Luís]

David Schultz wrote:
> On Tue, Jan 25, 2005, Bruce M Simpson wrote:
> 
>>If we could take a clean subsystem-by-subsystem approach to marshaling
>>kernel state to disk, that would be good. What gives me particular pain
>>here is dealing with things like the filesystem. How does one deal with
>>open files, etc, with pending I/O?
> 
> 
> You just write an image of physical memory to disk, and the data
> structures behind the open files come back exactly as they were
> before.  ;-)  The hard part, I think, is getting all the device
> drivers to understand how to reinitialize the hardware in exactly
> the same state it was in before the suspend.

     Yes!  This is where we need most rewriting.

> BTW, contrary to what Matt said, I don't think network
> connections are a big deal.  If you turn your computer on after a
> long plane flight to Tahiti, and the kernel still thinks you have
> active TCP connections, it will quickly discover that the
> remote host doesn't think so and take appropriate action.
> I'm pretty sure Windows doesn't do anything special with network
> connections, because a friend of mine says he manages to turn off
> his laptop, walk to the other side of a building and down a few
> floors, turn the laptop back on, and still be logged in to a
> remote server via SSH.

     If the keep alive packets did not shut the other side, and the 
network is the same, there's no need to shutdown the connection.  But if 
onde does hibernate, he must know that network connections may not 
survive.  Every network program that really cares for its connection 
will restart it if needed.

                                         Jonny

-- 
João Carlos Mendes Luís - Networking Engineer - jonny at jonny.eng.br