smokey's fork tests hangs?

Lange Norbert norbert.lange at andritz.com
Mon Mar 11 12:16:52 CET 2019



> -----Original Message-----
> From: Jan Kiszka <jan.kiszka at siemens.com>
> Sent: Freitag, 8. März 2019 16:23
> To: Lange Norbert <norbert.lange at andritz.com>; Xenomai
> (xenomai at xenomai.org) <xenomai at xenomai.org>
> Subject: Re: smokey's fork tests hangs?
>
> E-MAIL FROM A NON-ANDRITZ SOURCE: AS A SECURITY MEASURE, PLEASE
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>
> On 08.03.19 15:05, Lange Norbert wrote:
> >
> >
> >> -----Original Message-----
> >> From: Jan Kiszka <jan.kiszka at siemens.com>
> >> Sent: Freitag, 8. März 2019 14:59
> >> To: Lange Norbert <norbert.lange at andritz.com>; Xenomai
> >> (xenomai at xenomai.org) <xenomai at xenomai.org>
> >> Subject: Re: smokey's fork tests hangs?
> >>
> >> E-MAIL FROM A NON-ANDRITZ SOURCE: AS A SECURITY MEASURE,
> PLEASE
> >> EXERCISE CAUTION WITH E-MAIL CONTENT AND ANY LINKS OR
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> >>
> >> On 08.03.19 14:47, Lange Norbert wrote:
> >>>
> >>>>
> >>>> Not reproducible here with stable/3.0.x or next, and with
> >>>> ipipe-x86-
> >> 4.14.y.
> >>>> What are your parameters?
> >>>
> >>> Not entirely upstream, but based on ipipe-core-4.14.89-x86-2 and
> >>> xenomai master, the difference is contained in the rt_igb driver,
> >>> which is
> >> not even loaded.
> >>> Defconfig is attached.
> >>>
> >>> I mostly suspect glibc as the relevant difference, I am using
> >>> glibc-2.28-69-g1e5c5303a522764d7e9d2302a60e4a32cdb902f1.
> >>>
> >>> Looking at the strace the child process 1039 is stuck at
> >>> FUTEX_WAIT_PRIVATE, Don’t really know how to tackle this.
> >>
> >> Is this a regression? Then try bisecting the causing commit.
> >
> > Not really, I haven't ran the smokey suite often (and only for specific tests).
> > I use buildroot for my rootfs, so I have no easy way of swapping around
> glibc versions.
> > I have not encountered other issues outside of those tests.
> >
> > Which version of glibc is running on your end?
> >
>
> Mine is in fact old: 2.19. Colleagues are on Debian 9 with 2.24 where this used
> to work but was not tested recently against master.
>
> I haven't tried buildroot with Xenomai yet - is there a working 3.x recipe, and
> everything is out-of-the-box?

Yes, and thats both a blessing(easy to start with) and a curse(by defaults builds everything inc. toolchain, packages mostly available in 1 version).
It has a configuration system similar to the Kernel, getting to a xenomai userspace would take the following steps:

make O=/tmp/c defconfig
make O=/tmp/c menuconfig
make O=/tmp/c

You would have to change in menuconfig:
Target options: x86_64
Toolchain -> C library: glibc
Target packages -> Real-Time: xenomai (set cobalt + test utils, set version to 3.0.8)

(or you drop the attached file into configs/xenomai_defconfig and run 'make O=/tmp/c xenomai_defconfig')

And you would need to remove the patch in package/xenomai as it won't apply with 3.0.8.

> Regarding how to possibly debug this: If one thread is stuck, you could check
> if there are other threads in that application that may hold the lock. Or if the
> lock content is actually invalid and therefore blocking the caller (memoryC
> corruption). You should be able to read out the thread ID of the owner from
> a valid lock structure.

I don’t know what the fork+exec sequence should do. I only know libc waits forever for a private futex,
potentially synchronizing with a thread that has not been created yet.
As said, I haven’t encountered any other issues and I am not able to sink a lot time into something
that’s not a problem right now. I would still like to narrow down the cause.

Norbert
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