Subject: Re: Interrupt, interrupt threads, continuations, and kernel lwps
To: Bucky Katz <>
From: Bucky Katz <>
List: tech-kern
Date: 02/23/2007 13:43:37
David Laight <> writes:

> On Thu, Feb 22, 2007 at 10:33:36PM -0800, Bucky Katz wrote:
>> A wise man once told me that "if you're doing more work in
>> interrupt context than you can comfortably code in assembler in an
>> afternoon, you're doing too much work in interrupt context." ;)
> However you are going to have to execute the cpu cycles at some
> point, if the interrupt isn't going to schedule a process then you
> probably want to avoid the cost of the scheduling the deferred code.

Not all of them. If you do a top/bottom design with lockless
synchronization then you don't ever have to yield in interrupt context
and you never (rather than rarely) spin in interrupt context.

> Remembers the ISR code to drive a stepper motor graph plotter under
> RSX/11M (which expected the h/w ISR to just remove the IRQ and leave
> the rest of the code to some os work queue...)

Great. I've been supressing RSX memories for decades. thanks for the
image ;)