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 -
