Re: [Xenomai] testsuite segfaults on Ubuntu 16.04 with Xenomai 2.6.4

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On Thu, Mar 24, 2016 at 12:53:33PM +0100, Henning Schild wrote:
> On Thu, 24 Mar 2016 11:14:57 +0100
> Christoph Permes <christoph.permes@knapp.com> wrote:
> 
> > On 03/24/2016 10:51 AM, Gilles Chanteperdrix wrote:
> > > On Thu, Mar 24, 2016 at 10:38:29AM +0100, Christoph Permes wrote:  
> > >> Hi,
> > >>
> > >> I am experiencing problems getting Xenomai 2.6.4 running on Ubuntu
> > >> 16.04.
> > >>
> > >> My Xenomai applications and also some applications from the
> > >> testsuite (e.g. cyclictest, latency) keep crashing instantly with
> > >> a segfault.
> > >>
> > >> For instance, cyclictest crashes with the following backtrace:
> > >>
> > >> Thread 1 "cyclictest" received signal SIGSEGV, Segmentation fault.
> > >> 0xb7fb59f3 in xnarch_tsc_to_ns (ticks=16028154345163)
> > >> at ../../../src/include/asm-generic/xenomai/bits/timeconv.h:37
> > >> 37              return xnarch_llmulshft(ticks, tsc_scale,
> > >> tsc_shift); (gdb) bt #0  0xb7fb59f3 in xnarch_tsc_to_ns
> > >> (ticks=16028154345163)
> > >> at ../../../src/include/asm-generic/xenomai/bits/timeconv.h:37 #1
> > >> 0xb7fbfa9c in __wrap_clock_gettime (clock_id=1, tp=0x804c1f0
> > >> <start>) at clock.c:121 #2  0x08049cc3 in main (argc=1,
> > >> argv=0xbffff6a4) at cyclictest.c:587
> > >>
> > >> The backtrace of all other applications also leads to
> > >> xnarch_tsc_to_ns.
> > >>
> > >>
> > >> I am using
> > >> - Xenomai 2.6.4
> > >> - Linux 3.14.44 (see attachment for kernel configuration)
> > >> - ipipe-core-3.14.44-x86-10.patch
> > >>
> > >> which works without any issues on Ubuntu 14.04, so it seems to me
> > >> that the problem is related to the compiler or some system
> > >> libraries.
> > >>
> > >> I have also tried the prebuilt Xenomai packages from the Ubuntu
> > >> package repository as well as the latest 2.6 git head, different
> > >> I-Pipe patch (ipipe-core-3.14.44-x86-11.patch), but the problem is
> > >> still the same.
> > >>
> > >> With Xenomai 3.0.1 the testsuite seems to work, but for now I would
> > >> prefer staying with 2.6 as porting my applications to Xenomai 3
> > >> would take some more effort.
> > >>
> > >>
> > >> Can anyone point me into the right direction?  
> > > 
> > > xnarch_llmulshft is written in assembly, it probably lacks a
> > > constraint which causes bad code generation under register pressure
> > > (which is high on x86_32). You need to work at the assembly level to
> > > understand what is wrong and fix the assembly code. As a quick
> > > check, you may want to check 3.0 implementation of the same
> > > function, to see if it has already been fixed.
> > > 
> > > What is astonishing however, is that xnarch_llmulshft only uses
> > > registers to do some arithmetic operations, it should not
> > > dereference any pointer. I guess some argument lands on stack since
> > > x86_32 has so few registers. You may want to run a 64 bits OS if
> > > the machine is 64 bits.
> > >   
> > 
> > Just checked out the Xenomai 3 code, the change in commit
> > 5d313a256ff20a8ccdab6503e5f99b032ec9e6f1 seems to solve the problem
> > also in 2.6.4, the commit message suggests that it is gcc related.
> 
> Can you please send a patch to this list so the problem gets fixed
> mainline? Or maybe Philippe will backport the fix?

I will backport the fix. I plan to issue a 2.6.5 release soon. But
the plan is for it to be the last release in the 2.6 branch.

-- 
					    Gilles.
https://click-hack.org