Re: [fixed] [patch] Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+

Ingo Molnar
2008-06-06T17:34:30Z

* Patrick McManus <mcmanus@ducksong.com> wrote:

> When I apply the locking patch you (Ilpo) wrote, I cannot reproduce
> the error at all in the first 90 minutes of testing. I'll let the test
> run and update the list.
>
> I'm holding out hope that Ingo's report did not have the locking patch
> on the distcc server end - because it certainly makes a difference for
> me.

Hm, the distcc server had the full 3-patch-revert from Ilpo, was that
supposed to fix the problem too, indirectly?

The box is running that 3-patch revert right now as well:

phoenix:~> uptime
19:20:28 up 9:58, 2 users, load average: 7.75, 13.88, 30.95
phoenix:~> uname -a
Linux phoenix 2.6.26-rc4 #2352 SMP Fri Jun 6 09:18:07 CEST 2008 x86_64 x86_64 x86_64 GNU/Linux

... and i never saw a single hang today in the 10 hours of uptime this
box has. (and it built a good 500 kernel today) Nor any hang yesterday,
and that was a good 500 kernels too.

You can see it that the box built more than two thousand kernels in the
past few days alone, so it's a rather busy little bee. The other
testboxes built even more kernels - a quad box built and booted 2500
kernels:

#define UTS_VERSION "#2524 SMP PREEMPT Fri Jun 6 19:22:21 CEST 2008"

and i never saw a hang on that box either.

a third box has:

titan:~> uname -a
Linux titan 2.6.26-rc5-00002-g737697d-dirty #2557 SMP PREEMPT Fri Jun 6
19:24:00 CEST 2008 x86_64 x86_64 x86_64 GNU/Linux

(this is the one that showed the hang for the first time)

The total count of kernel bootups i did this week for -tip QA was
somewhere between five and ten thousand random build+bootups - and the
only time i got a hang was when i removed the 3-patch-revert
intentionally, on one of the boxes.

Maybe that 3-patch-revert just makes this locking bug a bit less likely
to trigger, by accident? Out tip test-setup is specialized to find
arch/x86 and scheduler bugs, not primarily to find networking bugs. (but
at this test volume, and given that it makes use of distcc, it will
trigger them too.)

i have a rather accurate timeline of when the hang first occured, do we
know the timeline of the introduction of the locking bug by any chance?
Which commit introduced it? (Ilpo's commit log does not say it)

Your test results are compelling nevertheless so i'll do a retest in any
case, with all boxes either running an older kernel or a kernel with the
locking fix.

Ingo