Messages in this thread | | | Date | Wed, 23 Sep 1998 10:15:15 +1000 | From | Richard Gooch <> | Subject | Re: Today Linus redesigns the networking driver interface (was Re: tulip driver in ...) |
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Linus Torvalds writes: > > > On Wed, 23 Sep 1998, Richard Gooch wrote: > > > > I don't understand why selectively marking/not marking a BH doesn't > > give you what you want. > > The problem with not marking the BH is that there would be no timeout. > > In contrast, marking the BH but asking the interrupt return code not > to do BH processing will still guarantee that the BH gets processed > eventually anyway: at the latest during the next timer tick, but > possibly long before that if we're idle.
Ah, OK, I see. I was working under the assumption that an interrupt handler would hold off marking its BH until it got a "marker" interrupt. The example Ted cited with PPP fit this: mark the BH when you get the last character in the frame. I guess not all handlers have the luxury of an end-of-frame marker, though.
BTW: if you're idling, that doesn't mean that BH's are called before the next timer tick. AFAIK do_bottom_half() is only called on return from syscall/interrupt and when rescheduling. Waiting for the next timer tick would be horrible for latency, though.
Regards,
Richard....
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