netdev - Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs. dev

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Message-Id: <20080821.005250.117238212.davem@davemloft.net>
Date:	Thu, 21 Aug 2008 00:52:50 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	jarkao2@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs.
 dev_deactivate() race

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Thu, 21 Aug 2008 17:16:34 +1000

> Actually, why do we even keep a netdev_queue pointer in a qdisc?
> A given qdisc can be used by multiple queues (which is why the
> lock was moved into the qdisc in the first place).
> 
> How about keeping a pointer directly to the root qdisc plus a
> pointer to the netdev (which seems to be the only other use for
> qdisc->dev_queue)? That way there won't be any confusion as to
> whether we want the sleeping or non-sleeping qdisc.

Not a bad idea at all.

The reason it's there is a left-over from earlier designs of my
multiqueue stuff, I thought we'd always multiplex the qdiscs to be
per-queue.  But once Patrick showed me we couldn't do that, we now
have shared qdiscs.

If I get a chance I'll work on this.  But to be honest given
Linus's temperment right now we're only going to be able to
merge one-liners to fix these kinds of problems and anything
more serious is going to be for net-next-2.6 only.
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