netdev - Re: [PATCH] pkt_sched: Destroy gen estimators under rtnl

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Message-ID: <20080819222329.GA10297@gondor.apana.org.au>
Date:	Wed, 20 Aug 2008 08:23:29 +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
Subject: Re: [PATCH] pkt_sched: Destroy gen estimators under rtnl_lock().

On Tue, Aug 19, 2008 at 06:48:31PM +0200, Jarek Poplawski wrote:
> 
> I can miss something, but probably it's needed in __netif_reschedule()

No this is a genuine bug.  However, it's also an old bug :) Even
with the locking and RCU barrier it could have occured.

> yet. Here is a scenario:
> 
> cpu1				cpu2
> dev_deactivate()
> dev_deactivate_queue()
> qdisc_reset()
> 				qdisc_run()
> 				qdisc_watchdog_schedule()
> 				(or hrtimer_restart in cbq)

We should add an aliveness check before scheduling the timer.  This
is the slow path so adding a check shouldn't hurt.

Thanks,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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