The critical section lock _can_ be held in these place.

The critical section lock _can_ be held in these place.

At least since hurd_thread_cancel can be called by another thread and lock our
critical lock.

http://bugs.debian.org/46859

“
Thomas suggested that there is no need to take the critical section
lock.  I believe that taking the critical section lock is necessary to
prevent the target thread from entering a signal handler.  Roland will
look into the problem.
”

Taking the critical section lock makes these assertions bogus.

It happens that hurd_thread_cancel is only called from libports and inside
/hurd/term so this is rare in practice.

A reproducer can be found here:

http://lists.gnu.org/archive/html/bug-hurd/2014-05/msg00025.html

2006-08-05  Samuel Thibault  <samuel.thibault@ens-lyon.org>

       * hurd/thread-cancel.c (hurd_thread_cancel): Do not assert that
       `&ss->critical_section_lock' is unlocked.
       * sysdeps/mach/hurd/jmp-unwind.c (_longjmp_unwind): Likewise, and take
       critical section lock before taking the sigstate lock.
       * sysdeps/mach/hurd/spawni.c (__spawni): Likewise.

Gbp-Pq: Topic hurd-i386
Gbp-Pq: Name tg-thread-cancel.diff