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

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

[Oleg Nesterov]

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.

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

[Roland McGrath]

> signal_struct->count in its current form must die.

Agreed.  This series
Acked-by: Roland McGrath <roland@redhat.com>

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

Another of many good reasons for...

> 	- 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.

Yes, and sighand too.  I think there will be quite a torrent of cleanup we
can do after that.

Remember too that we should really change de_thread() altogether.  It has
long-standing signal-losing races that we should fix.  Changing the
lifetime rules may complicate that, or not.  But they'll tie in together,
and when we do that we'll replace the notify_count again with something
else entirely.


Thanks,
Roland

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

[Veaceslav Falico]

On Wed, Mar 17, 2010 at 08:28:47PM +0100, Oleg Nesterov wrote:
> signal_struct->count in its current form must die.

Ack on this series.
Acked-by: Veaceslav Falico <vfalico@redhat.com>

--
Veaceslav