[openbeos] Re: Add-ons/Module problems/ideas??
- From: Timothy Covell <timothy.covell@xxxxxxxxxxx>
- To: openbeos@xxxxxxxxxxxxx, Isaac Yonemoto <ityonemo@xxxxxxxxxxxx>
- Date: Wed, 31 Jul 2002 20:28:58 -0400
On Wed July 31 2002 20:08, Isaac Yonemoto wrote:
> Is it possible to have a kernel that can reboot itself? I think I posted
> this on the suggestions list, but I didn't get much of a response.
>
> 1. The kernel suspends each thread, recording the priority of each thread
> as they are taken down.
>
> 2. The kernel takes the entire memory space and transfers it to a
> known position on disk.
>
> 3. The kernel records (whatever other critical information it needs).
>
> 4. The kernel shuts down. (either shutting down the machine, also, or
> rebooting the kernel).
>
> On bootup (if say, spacebar is pressed), then it boots up normally,
> clearing out all of the previously recorded information.
>
> Otherwise, after the FS is loaded, it transfers the entire memory space
> back up to the machine from disk, and whatever other information was
> transferred. Then it one-by-one turns on each thread.
>
> I guess there are a few important things that need to be addressed (what
> to do with semaphores floating about, thread_ids, port_ids, area_ids
> needing to be conserved, et cetera)...
>
> Are there real problems with this idea? Because, it seems to me, that
> implementing something like this would allow us to do reboot-less kernel
> upgrades, and neato instant-on features. Perhaps this belongs in
> glasselevator, but I don't see why something like this wouldn't be "R5
> compliant", binary or codewise.
>
> Isaac
Yes it is possible. Linux, for example, now has an experimental
suspend-to-disk implementation. I haven't tried it since the 2.5.x kernels
almost never compile completely. The interface isn't so simple because it
writes out the system state to a swap space. On reboot, one must give a
special resume flag to the kernel, otherwise the swap space will try to
initialize (and it's hard to pass flags with Grub, and somewhat still a bit
annoying with Lilo.). Also, after restoring, the swap space must be
reinitialized with mkswap and swapon. Also, I doubt that one could ever
return to the EXACT same state, especially with any kernel upgrades which
change drivers, API, etc. because I would expect a lot of core dumps and
even kernel panics.
--
timothy.covell@xxxxxxxxxxxx
Unix Systems Administrator
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