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SubjectRe: Today Linus redesigns the networking driver interface (was Re: tulip driver in ...)
Date
On Tue, 22 Sep 1998 17:27:36 +1000, 
Richard Gooch <rgooch@atnf.csiro.au> wrote:
>So a heuristic to avoid BH processing isn't really worthwhile, I now
>think, nor is a return flag from interrupt handlers saying "please
>don't process BH's now", since the (bh_active & bh_mask) test is good
>enough.
>The simple rule: "if you haven't registered/marked active a BH, then
>you aren't going to trigger BH processing, so don't worry about it"
>seems like the right thing.

Something that has been puzzling me about all of this selective do or
don't mark_bh(). If there is data to be processed then the BH must be
run eventually. When does the interrupt handler finally decide to
mark_bh()? The obvious way is on a later interrupt but what happens if
no more interrupts arrive? Extremely unlikely but possible.

The only other way to mark_bh() is something external to the interrupt
handler, say a timer. But that just complicates the code - is it worth
it? Does it really cost that much to run the BH mask?


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