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Date: Thu, 25 Jul 2013 09:01:40 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
Message-ID: <20130725090140.658f33f7@nehalam.linuxnetplumber.net>
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	<1374760580-12920-1-git-send-email-linus.luessing@web.de>
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Subject: Re: [Bridge] [PATCHv2] bridge: disable snooping if there is no
	querier
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To: Linus =?ISO-8859-1?B?TPxzc2luZw==?= <linus.luessing@web.de>
Cc: Cong Wang <amwang@redhat.com>, netdev@vger.kernel.org, bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Adam Baker <linux@baker-net.org.uk>, "David S. Miller" <davem@davemloft.net>, Herbert Xu <herbert@gondor.apana.org.au>

On Thu, 25 Jul 2013 15:56:20 +0200
Linus L=FCssing <linus.luessing@web.de> wrote:

> =20
> +static void br_multicast_update_querier_timer(struct net_bridge *br,
> +					      unsigned long max_delay)
> +{
> +	if (!timer_pending(&br->multicast_querier_timer))
> +		atomic64_set(&br->multicast_querier_delay_time,
> +			     jiffies + max_delay);
> +
> +	mod_timer(&br->multicast_querier_timer,
> +		  jiffies + br->multicast_querier_interval);
> +}
> +

Isn't this test racing with timer expiration.

static void br_multicast_update_querier_timer(struct net_bridge *br,
					      unsigned long max_delay)
{
	if (!timer_pending(&br->multicast_querier_timer))
		atomic64_set(&br->multicast_querier_delay_time,
			     jiffies + max_delay);
What if timer completes here?

	mod_timer(&br->multicast_querier_timer,
		  jiffies + br->multicast_querier_interval);
}


And another race if timer goes off?

static void br_multicast_update_querier_timer(struct net_bridge *br,
					      unsigned long max_delay)
{
	if (!timer_pending(&br->multicast_querier_timer))
		atomic64_set(&br->multicast_querier_delay_time,
			     jiffies + max_delay);
Timer fires here...?

	mod_timer(&br->multicast_querier_timer,
		  jiffies + br->multicast_querier_interval);
}