Re: [patch 1/6] mmu_notifier: Core code

[Andrea Arcangeli]

On Tue, Jan 29, 2008 at 06:29:10PM -0800, Christoph Lameter wrote:
> +void mmu_notifier_release(struct mm_struct *mm)
> +{
> +	struct mmu_notifier *mn;
> +	struct hlist_node *n, *t;
> +
> +	if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) {
> +		rcu_read_lock();
> +		hlist_for_each_entry_safe_rcu(mn, n, t,
> +					  &mm->mmu_notifier.head, hlist) {
> +			hlist_del_rcu(&mn->hlist);

This will race and kernel crash against mmu_notifier_register in
SMP. You should resurrect the per-mmu_notifier_head lock in my last
patch (except it can be converted from a rwlock_t to a regular
spinlock_t) and drop the mmap_sem from
mmu_notifier_register/unregister.
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