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From: Oleg Nesterov on 17 Mar 2010 15:40
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.

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