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Date: Fri, 7 Apr 2006 15:56:19 -0700
From: Andrew Morton <akpm@osdl.org>
To: oleg@tv-sign.ru, ebiederm@xmission.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH rc1-mm] de_thread: fix deadlockable process addition
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Andrew Morton <akpm@osdl.org> wrote:
>
> Oleg Nesterov <oleg@tv-sign.ru> wrote:
> >
> > -		if (likely(p->tasks.prev != LIST_POISON2))
> > +		if (likely(p->tasks.prev != LIST_POISON2)) {
> 
> argh.
> 
> c'mon guys, we can't put a dependency on list_head poisoning into generic
> code.
> 

A suitable fix might be to add a new list_del_poison() (or
list_del_rcu_something()?) and use that everywhere.

But it should use a different poisoning pattern, so we know that the kernel
will still work correctly when someone removes the list_head debugging.