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From: John Stultz <john.stultz@linaro.org>
To: Trevor Cordes <trevor@tecnopolis.ca>
Cc: lkml <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Josh Boyer <jwboyer@redhat.com>
Subject: Re: regression in ktime.h circa 3.16.0-rc5+ breaks lirc irsend, bad commit 166afb64511
Date: Thu, 30 Apr 2015 09:35:04 -0700	[thread overview]
Message-ID: <CALAqxLVTUSmw=zvyLde3BRfQMFSmePgXoFq+yD-pVFd1zkua6Q@mail.gmail.com> (raw)
In-Reply-To: <20150429232721.59b89cb1@pog.tecnopolis.ca>

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

  parent reply	other threads:[~2015-04-30 16:35 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-23 16:57 regression in ktime.h circa 3.16.0-rc5+ breaks lirc irsend, bad commit 166afb64511 Trevor Cordes
2015-04-30  4:27 ` Trevor Cordes
2015-04-30 10:53   ` One Thousand Gnomes
2015-04-30 16:35   ` John Stultz [this message]
2015-05-01 10:02     ` Trevor Cordes
2015-05-01 17:31       ` John Stultz
2015-05-01 18:29         ` Nicolas Pitre
2015-05-01 18:51           ` John Stultz

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