From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 5/6] NLM: Convert lockd to use kthreads
Date: Wed, 9 Jan 2008 17:45:06 +0000
Message-ID: <20080109174506.GB30523@infradead.org>
References: <1199820798-5289-1-git-send-email-jlayton@redhat.com> <1199820798-5289-2-git-send-email-jlayton@redhat.com> <1199820798-5289-3-git-send-email-jlayton@redhat.com> <1199820798-5289-4-git-send-email-jlayton@redhat.com> <1199820798-5289-5-git-send-email-jlayton@redhat.com> <1199820798-5289-6-git-send-email-jlayton@redhat.com>
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Cc: akpm@linux-foundation.org, neilb@suse.de,
	linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
To: Jeff Layton <jlayton@redhat.com>
In-Reply-To: <1199820798-5289-6-git-send-email-jlayton@redhat.com>
Sender: linux-nfs-owner@vger.kernel.org

On Tue, Jan 08, 2008 at 02:33:17PM -0500, Jeff Layton wrote:
> -	struct svc_serv *	serv;
> -	int			error = 0;
> +	struct svc_serv *serv;
> +	struct svc_rqst *rqstp;
> +	int		error = 0;
>  
>  	mutex_lock(&nlmsvc_mutex);
>  	/*
>  	 * Check whether we're already up and running.
>  	 */
> -	if (nlmsvc_pid) {
> +	if (nlmsvc_task) {
>  		if (proto)
>  			error = make_socks(nlmsvc_serv, proto);

While equivalent I think it would be clener to check for nlmsvc_serv
above as that'swhat we're passing to make_socks.  But I think the whole
of lockd_up could use a little makeover, but that's for later.

>  void
>  lockd_down(void)
>  {
>  	mutex_lock(&nlmsvc_mutex);
>  	if (nlmsvc_users) {
>  		if (--nlmsvc_users)
>  			goto out;
> +	} else {
> +		printk(KERN_ERR "lockd_down: no users! task=%p\n",
> +			nlmsvc_task);
> +		BUG();
>  	}
> +	if (!nlmsvc_task) {
> +		printk(KERN_ERR "lockd_down: no lockd running.\n");
> +		BUG();
>  	}
> +	kthread_stop(nlmsvc_task);

I think all this user/foo checking here should be BUG_ONs as it's quite
fatal errors.

e.g.

void
lockd_down(void)
{
 	mutex_lock(&nlmsvc_mutex);

	BUG_ON(!nlmsvc_task);
	BUG_ON(!nlmsvc_users);

	if (!--nlmsvc_users)
		kthread_stop(nlmsvc_task);
	mutex_unlock(&nlmsvc_mutex);
}


same applies for similar checks in lockd_up aswell.