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Subject: Re: [PATCH] x86: Add a list for custom page fault handlers.
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Pekka Paalanen <pq@iki.fi>
Cc: mingo@redhat.com, linux-kernel@vger.kernel.org,
       Jan Beulich <jbeulich@novell.com>
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References: <20080127185238.4bcac54b@daedalus.pq.iki.fi>
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Date: Sun, 27 Jan 2008 22:03:31 +0100
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On Sun, 2008-01-27 at 18:52 +0200, Pekka Paalanen wrote:

> +void unregister_page_fault_handler(struct pf_handler *old_pfh)
> +{
> +	might_sleep();
> +	spin_lock(&pf_handlers_writer);
> +	hlist_del_rcu(&old_pfh->hlist);
> +	spin_unlock(&pf_handlers_writer);
> +	synchronize_rcu();
> +}
> +EXPORT_SYMBOL_GPL(unregister_page_fault_handler);

Could you remove that sync_rcu() call and put in the comments that the
calling function is to take care of proper freeing.

sync_rcu() is a _very_ expensive call, and oft time it is not needed in
favour of call_rcu().