Bug#987587: libpango1.0-udeb: hangs the installer in various situations

[Chris Hofstaedtler]

* Cyril Brulebois <kibi at debian.org> [210430 09:47]:
> Anyway, looking at the diffstat between 1.43.0 (last known good) and
> 1.44.4 (first known bad), we have this:
>  179 files changed, 19157 insertions(+), 7045 deletions(-)
> 
> Between 1.43.0 and 1.44 (if it were an earlier known bad):
>  165 files changed, 11006 insertions(+), 6766 deletions(-)
> 
> which is a huge diff still.

Indeed :-(

> From your earlier report on #987449[1], something around
> pango_default_break seemed to be happening. (In passing, I'd love to
> learn how you generated it so that I can try my luck with #987377.)

Quick steps:
- I created a Debian bullseye install with a kernel version matching
  the installer, and also installed linux-perf(-5.10)
- From the running, already stuck installer, I mounted the existing
  install, did the whole mount --bind stuff for sys, proc, dev.
  I cannot remember if one needs to actually chroot.
- And then its mostly `perf top` and/or `perf record` + `perf
  report`. The former gives you an immediate view, while the latter
  writes into a file which you can look at later.

Having more debug symbols would have been useful, but I did not
manage to set that up.

Chris