Re: Migration threads

[olafBuddenhagen]

Hi,

On Sun, Dec 26, 2010 at 10:27:30AM +0100, Richard Braun wrote:

> >From what I understand of the Hurd history, GNU Mach is based on Mach 4.
> I read that this version was intended to include the result of research
> work made at the university of Utah, the most important being thread
> migration (for those not familiar with the concept, it means that
> threads running in client tasks "migrate" into server tasks when
> performing sync RPC). There is actually code about that in GNU Mach,
> but I'm wondering if it's actually used in the Hurd. I couldn't find
> anything related to this in the userspace servers, but the interface
> change could be light, and I might have missed them. Does anyone know if
> the Hurd servers actually use thread migration ?

While I don't *know*, I have looked at most of the client- and
server-side marshalling, multiplexing, and thread management code; and
I'm pretty confident there is nothing about thread migration there...
But then, I haven't really checked how thread migration works exactly --
so I might be missing something :-)

Some of the RPC management code in Hurd is pretty complex. (Evidently
the Hurd's use of Mach IPC is different from what the Mach inventors
envisioned -- which is part of the reason why I believe that to get
forward, we have to abandon Mach compatibility.) Corner cases like RPC
cancellation, server death etc. will need some serious consideration I
guess.

Fredrik looked into the RPC cancellation and related stuff quite a bit
recently, so I guess he might have a better idea about this...

-antrik-