From: David Miller <davem@davemloft.net>
To: dingtianhong@huawei.com
Cc: gaofeng@cn.fujitsu.com, yoshfuji@linux-ipv6.org, joe@perches.com,
vfalico@redhat.com, netdev@vger.kernel.org
Subject: Re: [PATCH net] net: neighbour: add neighbour dead check for neigh_timer_handler()
Date: Wed, 04 Dec 2013 01:36:38 -0500 (EST) [thread overview]
Message-ID: <20131204.013638.2211412920346095879.davem@davemloft.net> (raw)
In-Reply-To: <529EC95A.5080908@huawei.com>
From: Ding Tianhong <dingtianhong@huawei.com>
Date: Wed, 4 Dec 2013 14:19:06 +0800
> Yes, you are right, but when the timer is running and prior to get
> the neigh->lock, the refcnt could be dec to 0, you could not stop it
> by existing mechanism.
>
> the refcnt of neighbour could only be inc by these actions:
>
> 1.create neighbour, the refcnt will be set to 1.
> 2.add timer, the refcnt++.
> 3.neigh_lookup, if found the neigh, refcnt++.
The refcnt cannot dec to 0 if the timer is running, that's why
the last action of the timer handler is neigh_release().
The timer handler always holds a reference to the neighbour entry for
which it is running, that is why it must always release it.
If it can dec to 0, then this neigh_release() call in the timer
handler is illegal. But it is not.
prev parent reply other threads:[~2013-12-04 6:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 13:48 [PATCH net] net: neighbour: add neighbour dead check for neigh_timer_handler() Ding Tianhong
2013-12-03 15:03 ` Hannes Frederic Sowa
2013-12-04 1:36 ` Ding Tianhong
2013-12-03 16:28 ` Eric Dumazet
2013-12-04 1:59 ` Ding Tianhong
2013-12-03 16:37 ` David Miller
2013-12-04 2:37 ` Gao feng
2013-12-04 4:04 ` Ding Tianhong
2013-12-04 4:21 ` David Miller
2013-12-04 6:19 ` Ding Tianhong
2013-12-04 6:27 ` Eric Dumazet
2013-12-04 9:16 ` Ding Tianhong
2013-12-04 10:10 ` Gao feng
2013-12-04 15:24 ` Eric Dumazet
2013-12-05 0:32 ` Gao feng
2013-12-05 3:17 ` Ding Tianhong
2013-12-18 6:37 ` Ding Tianhong
2013-12-18 7:51 ` Hannes Frederic Sowa
2013-12-18 8:19 ` Ding Tianhong
2013-12-18 8:41 ` Hannes Frederic Sowa
2013-12-18 8:57 ` Ding Tianhong
2013-12-18 9:28 ` Hannes Frederic Sowa
2013-12-18 10:02 ` Ding Tianhong
2013-12-18 10:21 ` Hannes Frederic Sowa
2013-12-18 11:57 ` Ding Tianhong
2013-12-18 14:27 ` Hannes Frederic Sowa
2013-12-18 15:12 ` Ding Tianhong
2013-12-18 15:46 ` Hannes Frederic Sowa
2013-12-19 3:32 ` Ding Tianhong
2013-12-04 6:36 ` David Miller [this message]
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