Re: [patch 1/9] EMM Notifier: The notifier calls

From: Peter Zijlstra
Date: Tue Apr 01 2008 - 17:31:05 EST


(Christoph, why are your CCs so often messed up?)

On Tue, 2008-04-01 at 13:55 -0700, Christoph Lameter wrote:
> plain text document attachment (emm_notifier)

> +/* Register a notifier */
> +void emm_notifier_register(struct emm_notifier *e, struct mm_struct *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);
> +}
> +EXPORT_SYMBOL_GPL(emm_notifier_register);
> +
> +/* Perform a callback */
> +int __emm_notify(struct mm_struct *mm, enum emm_operation op,
> + unsigned long start, unsigned long end)
> +{
> + struct emm_notifier *e = rcu_dereference(mm)->emm_notifier;
> + int x;
> +
> + while (e) {
> +
> + if (e->callback) {
> + x = e->callback(e, mm, op, start, end);
> + if (x)
> + return x;
> + }
> + /*
> + * emm_notifier contents (e) must be fetched after
> + * the retrival of the pointer to the notifier.
> + */
> + e = rcu_dereference(e)->next;
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(__emm_notify);
> +#endif

Those rcu_dereference()s are wrong. They should read:

e = rcu_dereference(mm->emm_notifier);

and

e = rcu_dereference(e->next);



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/