Re: v3.13-rc6+ regression (ARM board)

From: Uwe Kleine-König
Date: Thu Jan 02 2014 - 05:15:12 EST

Hello Krzysztof,

On Thu, Jan 02, 2014 at 11:02:44AM +0100, Krzysztof HaÅasa wrote:
> >> There seems to be a regression in v3.13-rc6+ (up to current tip =
> >> 71ce176ee6ed1735b9a1160a5704a915d13849b1).
> >>
> >> Board is Gateworks Cambria, CPU Intel IXP435 ARM big endian, gcc 4.7.3.
> >> The board boots correctly and works (shell mostly, and SSHD) for about
> >> 50 seconds. After 52-54 seconds, it frozes dead without any console
> >> (UART) output.
> >>
> >> Bisecting shows 5e30025a319910695f5010dc0fb53a23299da14d as the first
> >> bad commit. Interestingly it's a merge:
> Reverting 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 on top of current tip
> (9a0bb2966efbf30a71c128c3af63307d8b5f5fc0) fixes my issue.
> What now?
> 1ca7d67cf5d5a2aef26a8d9afd789006fa098347:
> seqcount: Add lockdep functionality to seqcount/seqlock structures
> Currently seqlocks and seqcounts don't support lockdep.
> After running across a seqcount related deadlock in the timekeeping
> code, I used a less-refined and more focused variant of this patch
> to narrow down the cause of the issue.
> This is a first-pass attempt to properly enable lockdep functionality
> on seqlocks and seqcounts.
> Since seqcounts are used in the vdso gettimeofday code, I've provided
> non-lockdep accessors for those needs.
> I've also handled one case where there were nested seqlock writers
> and there may be more edge cases.
> Comments and feedback would be appreciated!
So it seems to be that 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 doesn't
like to be combined with some other commit from
What you can do is:

git bisect start 5e30025a319910695f5010dc0fb53a23299da14d^ b8a216269ec0ce2e961d32e6d640d7010b8a818e

The bad commit is the tip of Linus' tree when he created the bad merge
commit. The good one is the base of the merged tree. To check if a tree
is good or bad do:

git merge --no-commit 5e30025a319910695f5010dc0fb53a23299da14d^2
test test test
git reset --hard
git bisect good ... or ... git bisect bad

That should find the commit that makes your board break in combination
with 1ca7d67cf5d5a2aef26a8d9afd789006fa098347.

Best regards

Pengutronix e.K. | Uwe Kleine-KÃnig |
Industrial Linux Solutions | |
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