Bug#721421: libdevel-bt-perl: FTBFS on armel, hurd-i386, kfreebsd-amd64

[Niko Tyni]

On Thu, Sep 25, 2014 at 03:49:20PM +0200, Leon Timmermans wrote:
> On Tue, Sep 23, 2014 at 9:59 PM, Niko Tyni <ntyni at debian.org> wrote:
> 
> > I also had a look at the mips one, and there the problem doesn't seem
> > to be with the backtrace, as running gdb separately works as expected.
> > However, running perl with -d:bt doesn't seem to do anything. It looks
> > like the host is just too slow; inserting a 'sleep(1)' just before the
> > "thread apply all backtrace" command in stack_trace() fixes it for
> > me. Perhaps the code should just check that the fd is ready for writing?
> >
> 
> This should not matter. Pipes are buffered at a kernel level. This is not
> making sense to me.

Right. Sorry for not looking into it better.

The problem apparently happens when the timeout in the select loop
(one second) triggers before execvp() has been called.

I can reproduce a similar "race" on my x86_64 machine by inserting a
sleep(1) call right before the execvp() call.

I still haven't got to the bottom of it, but it looks like the gdb
output is lost somewhere with select() timeouting (and returning zero)
on subsequent calls too even though gdb has happily written to the pipe.

Will continue investigation.
-- 
Niko Tyni   ntyni at debian.org