Re: A small article about the Hurd on L4

[Espen Skoglund]

[Wolfgang Jährling]
> Hi!
> I have written down some information about the port of the Hurd to
> L4.  You can find it at <http://www.8ung.at/shell/l4-port.html>.
> Note the beautiful logo on the web page!

I see that you've mentioned interrupt sharing as a problem for device
drivers.  I don't really see your point here.  With the current X.2
API you can either 1) implement an interrupt distributor thread which
forwards the interruption IPC to the appropriate drivers and handles
the interrupt acking/unmasking, or 2) implement interrupt chaining
where you use propagation to hand off the interrupt to the next driver
in the chain if the current driver can not handle the interrupt.  By
using propagation the next driver in the chain will then be able to do
interrupt acking/unmasking.

Using the latter scheme there is no extra overhead with interrupt
sharing for the first driver in the chain.  The drivers later down in
the chain will of course take a performance hit, though, but if you
have multiple performance critical drivers sharing the same interrupt
line you'd better try to reconfigure your system anyway.

        eSk