[PATCH 1/3] restart: make sure all tasks are in sys_restart

[Oren Laadan]

There is no need the add another sync point at the beginning of
restart.

The bug was elsewhere - in reparent_thread() the code tested
the child's flags for PF_RESTARTING instead of the parent's.

Oren.

Serge E. Hallyn wrote:
> Make sure that all prepared tasks are in sys_restart before the
> coordinator proceeds.  Otherwise, it was possible for the last
> task actually in sys_restart to sync before the straggler was in
> sys_restart, sending that task a signal and causing that task to
> exit.  Then since there are not enough tasks completing restart,
> the restart operation ends up hanging, waiting for the killed task.
> 
> Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
> ---