Philippe Gerum authored May 24, 2021 and Jan Kiszka committed May 25, 2021

The offset field we receive from the kernel in a vfile next() handler
must progress in order for the loop to stop properly, independently
from our own tracking of the end-of-list condition.

Bug is reproducible by running two loops in parallel:

- one continuously spawning an application which creates a few tenths
of threads (10-20 would suffice) before exiting shortly after.

- another one continuously reading from /proc/xenomai/sched/{threads,
  stat, acct}.

At some point, the vfile handler should cause a kernel crash.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>