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    SubjectRe: [PATCH 2 of 9] Core of mmu notifiers
    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.



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