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Subject: Re: [RFC][PATCH 2/6] x86, nmi: create new NMI handler routines
From: Peter Zijlstra <peterz@infradead.org>
To: Don Zickus <dzickus@redhat.com>
Cc: x86@kernel.org, Andi Kleen <andi@firstfloor.org>,
        Robert Richter <robert.richter@amd.com>, ying.huang@intel.com,
        LKML <linux-kernel@vger.kernel.org>, jason.wessel@windriver.com
Date: Mon, 22 Aug 2011 16:16:20 +0200
In-Reply-To: <1313786266-9585-3-git-send-email-dzickus@redhat.com>
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	 <1313786266-9585-3-git-send-email-dzickus@redhat.com>
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On Fri, 2011-08-19 at 16:37 -0400, Don Zickus wrote:
> +static struct nmiaction *__free_nmi(unsigned int type, const char *name)
> +{
> +       struct nmi_desc *desc = nmi_to_desc(type);
> +       struct nmiaction *n, **np = &(desc->head);
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&desc->lock, flags);
> +
...
> +
> +       spin_unlock_irqrestore(&desc->lock, flags);
> +       synchronize_rcu();
> +       return *np;
> +}

> +void unregister_nmi_handler(unsigned int type, const char *name)
> +{
> +       kfree(__free_nmi(type, name));
> +}

This code is weird.. why not have the kfree() in __free_nmi(), also why
use sync_rcu() and not use kfree_rcu()?

> +EXPORT_SYMBOL_GPL(unregister_nmi_handler); 

*g*, so binary modules can register an NMI handler, but can't unregister
it..?