Re: [9fans] 9vx, kproc and *double sleep*

[ron minnich <rminnich@gmail.com>]

There's kind of an interesting similarity here to what I had to deal
with on the Xen port.

So, a few random thoughts, probably useless, from early problems of
this sort I've had.

- in Linux parlance, Plan 9 is a "preemptible" kernel. Interrupt
handlers can be interrupted, so to speak. Except for the clock
interrupt handler: you have to check the interrupt number to make sure
you are not pre-empting the clock interrupt handler. Sorry if I'm not
saying this very well. On Xen and lguest I had to make sure of this (I
mention this in the lguest port talk slides)
- splhi -- it's not a true splhi in some sense; is it possible that
some code is sneaking in and running even when you splhi()? Could this
explain it?
- What other aspect of the transition from hardware to
software-in-sandbox might explain a non-premptible bit of code getting
pre-empted?

OK, back to fixing my 1990 civic :-)

ron
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