[ofa-general] Re: [patch 02/10] emm: notifier logic

[Andrea Arcangeli]

On Fri, Apr 04, 2008 at 03:30:50PM -0700, Christoph Lameter wrote:
> +	mm_lock(mm);
> +	e->next = mm->emm_notifier;
> +	/*
> +	 * The update to emm_notifier (e->next) must be visible
> +	 * before the pointer becomes visible.
> +	 * rcu_assign_pointer() does exactly what we need.
> +	 */
> +	rcu_assign_pointer(mm->emm_notifier, e);
> +	mm_unlock(mm);

My mm_lock solution makes all rcu serialization an unnecessary
overhead so you should remove it like I already did in #v11. If it
wasn't the case, then mm_lock wouldn't be a definitive fix for the
race.

> +		e = rcu_dereference(e->next);

Same here.