Re: [RFC,PATCH] Use RCU to protect tasklist for unicast signals

["Paul E. McKenney" <paulmck@us.ibm.com>]

On Fri, Aug 12, 2005 at 12:51:17PM +0400, Oleg Nesterov wrote:
> Paul E. McKenney wrote:
> >
> > --- linux-2.6.13-rc4-realtime-preempt-V0.7.53-01/fs/exec.c	2005-08-11 11:44:55.000000000 -0700
> > +++ linux-2.6.13-rc4-realtime-preempt-V0.7.53-01-tasklistRCU/fs/exec.c	2005-08-11 12:26:45.000000000 -0700
> > [ ... snip ... ]
> > @@ -785,11 +787,13 @@ no_thread_group:
> >  		recalc_sigpending();
> > 
> > +		oldsighand->deleted = 1;
> > +		oldsighand->successor = newsighand;
> 
> I don't think this is correct.
> 
> This ->oldsighand can be shared with another CLONE_SIGHAND
> process and will not be deleted, just unshared.
> 
> When the signal is sent to that process we must use ->oldsighand
> for locking, not the oldsighand->successor == newsighand.

Hmmm...  Sounds like I mostly managed to dig myself in deeper here.

Back to the drawing board...

						Thanx, Paul
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