Re: [Libunwind-devel] UNW_EINVAL stepping past _L_lock_686 in pthread_mutex_lock

[Arun Sharma]

On Fri, Sep 26, 2014 at 2:15 PM, Jared Cantwell
<address@hidden> wrote:
> I have reproduced this on ubuntu 14.04 and 13.10.  Configuration
> information below.  I've also tested on 3.14 kernel and eglibc 2.18
> without any luck.  Arun, if my test passes for you on 13.10 can you
> provide information on your setup so I can compare?

ubuntu 13.10
3.11.0-12-generic
eglibc 2.17-93ubuntu4
g++ 4.8.1-10ubuntu8

I can't tell which version of libunwind you tested. 1.1 is likely to
have bugs that have since been fixed.

>
> Does the fact that gdb can unwind this stack mean anything?  Like that
> the unwind information is in libpthread in some form that libunwind
> doesn't quite understand?

This strongly suggests the unwind info is there, but your version of
libunwind is unable to find it.

There is also a possibility that gdb has a heuristic that works in the
absence of unwind info, but libunwind's heuristic doesn't work.

Steps I used to test:

cd libunwind; // commit id 781d5d5
make DESTDIR=/tmp/foo install
g++ unwind_repro.cpp -o unwind_repro
/tmp/foo/usr/local/lib/libunwind.a -llzma -lpthread
./unwind_repro // ran it 10 times

 -Arun