Message-ID: <43F4EBAF.D9BFEA13@tv-sign.ru>
Date: Fri, 17 Feb 2006 00:16:31 +0300
From: Oleg Nesterov <oleg@tv-sign.ru>
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To: paulmck@us.ibm.com
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Roland McGrath <roland@redhat.com>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 1/2] fix kill_proc_info() vs CLONE_THREAD race
References: <43E77D3C.C967A275@tv-sign.ru> <20060214223214.GG1400@us.ibm.com> <43F3352C.E2D8F998@tv-sign.ru> <43F37D54.4D0AAEFD@tv-sign.ru> <20060216191932.GE1296@us.ibm.com>
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"Paul E. McKenney" wrote:
> 
> > After that we don't need tasklist_lock to iterate over the thread
> > list, and we can simplify things, see for example do_sigaction()
> > or sys_times().
> 
> The above proposal would require that we hold siglock during the
> traversal, correct?

Yes, of course.

>                     Is that reasonable for non-signal-related traversals?
> Or were you thinking of making this change only for signal code?

Yes, I think it may be useful for non-signal-related traversals.

Currently we need tasklist_lock in order to use next_thread().
I beleive, we can migrate to rcu_read_lock+spinlock(sighand)
in most cases.

Well, next_thread() itself is safe already, but it can return
already zapped threads.

Oleg.
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