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Message-ID: <20080821120112.GA7705@gondor.apana.org.au>
Date: Thu, 21 Aug 2008 22:01:12 +1000
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Jarek Poplawski <jarkao2@...il.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
denys@...p.net.lb
Subject: Re: [PATCH] pkt_sched: Destroy gen estimators under rtnl_lock().
On Thu, Aug 21, 2008 at 11:55:22AM +0000, Jarek Poplawski wrote:
>
> Sure, here is a scenario:
>
> cpu1 cpu2
> rtnl_lock()
> qdisc_graft()
> // parent != NULL
> ->cops-graft()
> notify_and_destroy() qdisc_run()
> spin_lock(root_lock)
> qdisc_destroy(old) dequeue_skb()
> tbf_dequeue()
> qdisc_tree_decrease_qlen()
> qdisc_lookup()
> //deleting from qdisc_sleeping->list //walking qdisc_sleeping->list
> //under rtnl_lock() only //under qdisc root_lock only
> list_del(qdisc->list) list_for_each_entry(txq_root)
Good catch. Longer term we should fix it so that it doesn't do
the silly lookup at run-time. In fact we'll be getting rid of
requeue so there will be no need to do this in TBF at all.
However, for now please create a patch to put a pair of root locks
around the list_del in qdisc_destroy.
Thanks,
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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