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

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Message-Id: <20080818.171124.192743795.davem@davemloft.net>
Date:	Mon, 18 Aug 2008 17:11:24 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	jarkao2@...il.com, netdev@...r.kernel.org, denys@...p.net.lb
Subject: Re: [PATCH] pkt_sched: Destroy gen estimators under rtnl_lock().

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Tue, 19 Aug 2008 10:05:51 +1000

> On Mon, Aug 18, 2008 at 04:54:11PM -0700, David Miller wrote:
> > 
> > Yep, and that's the lock debugging thing which is triggering now.
> > Likely what I'll do is simply reinstate RCU but only for the freeing
> > of the memory, nothing more.
> > 
> > This keeps everything doing destruction under RTNL as desired,
> > yet fixes the "we're holding lock that's being freed" problem.
> 
> Is this the problem with dev_shutdown freeing the qdisc while
> holding its lock?
> 
> Couldn't we just drop the lock before calling qdisc_destroy?
> 
> dev_shutdown can only be called after dev_deactivate, as such
> all qdisc users should have disappeared by now (and if they
> haven't, our waiting loop in dev_deactivate didn't work and
> we should fix that).

Yep, that's another possible approach.

Especially since we've bullet-proof'd dev_deactivate(), there
should be absolutely no more references to the qdisc any
longer.

I'll look into doing it this way, thanks.
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