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    SubjectRe: regression in ktime.h circa 3.16.0-rc5+ breaks lirc irsend, bad commit 166afb64511
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    On Wed, Apr 29, 2015 at 9:27 PM, Trevor Cordes <trevor@tecnopolis.ca> wrote:
    > Sorry for the top-posting; Josh Boyer suggested I re-mail this mail
    > from last month which didn't get any replies. I'm still having this
    > weird kernel bug affecting me and I've bisected it down to like 2-4
    > lines of code. (I've thought more about my theory regarding
    > unsigned/signed below and it's probably wrong, so ignore my
    > prognosticating.) Please see my rhbz link near the bottom for the full
    > details.

    Thanks so much for the report and all the effort to chase down this regression!

    From your description it does seem like some sort of edge case problem
    w/ the 32bit ktime_divns(), but I don't see it right off, and I agree
    with Alan to do both calculations and print out warn when that
    happens.

    There's also not a ton of users of that function, but ktime_us_delta()
    is used in drivers/media/rc/ir-lirc-codec.c, which makes use of it in
    ir_lirc_transmit_ir().

    We should instrument that to see if its calculating negative deltas.

    I'll send you a debug patch to do the above.

    thanks
    -john


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