[ofa-general] Re: [PATCH 2 of 9] Core of mmu notifiers

Christoph Lameter
2008-04-14T19:57:00Z

On Tue, 8 Apr 2008, Andrea Arcangeli wrote:

> + /*
> + * Called when nobody can register any more notifier in the mm
> + * and after the "mn" notifier has been disarmed already.
> + */
> + void (*release)(struct mmu_notifier *mn,
> + struct mm_struct *mm);

Hmmm... The unregister function does not call this. Guess driver calls
unregister function and does release like stuff on its own.

> + /*
> + * invalidate_range_start() and invalidate_range_end() must be
> + * paired. Multiple invalidate_range_start/ends may be nested
> + * or called concurrently.
> + */

How could they be nested or called concurrently?

> +/*
> + * mm_users can't go down to zero while mmu_notifier_unregister()
> + * runs or it can race with ->release. So a mm_users pin must
> + * be taken by the caller (if mm can be different from current->mm).
> + */
> +int mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> + struct mm_lock_data *data;
> +
> + BUG_ON(!atomic_read(&mm->mm_users));
> +
> + data = mm_lock(mm);
> + if (unlikely(IS_ERR(data)))
> + return PTR_ERR(data);
> + hlist_del(&mn->hlist);
> + mm_unlock(mm, data);
> + return 0;

Hmmm.. Ok, the user of the notifier does not get notified that it was
unregistered.