[PATCH 0/4] signal_struct->count must die, initial changes

[Oleg Nesterov <oleg@redhat.com>]

signal_struct->count in its current form must die.

	- it has no reasons to be atomic_t

	- it looks like a reference counter, but it is not

	- otoh, we really need to make task->signal refcountable,
	  just look at the extremely ugly task_rq_unlock_wait()
	  called from __exit_signals().

	- we should change the lifetime rules for task->signal,
	  it should be pinned to task_struct. We have a lot of
	  code which can be simplified after that.

	- it is not needed! while the code is correct, any usage
	  of this counter is artificial, except fs/proc uses it
	  correctly to show the number of threads.

This series removes the usage of sig->count from exit pathes.

Oleg.