From: Patrick McHardy <kaber@trash.net>
To: Stephen Hemminger <shemminger@osdl.org>
Cc: "David S. Miller" <davem@davemloft.net>,
netdev@oss.sgi.com, netem@osdl.org
Subject: Re: [PATCH] (3/3) netem: adjust parent qlen when duplicating
Date: Wed, 04 May 2005 01:35:29 +0200 [thread overview]
Message-ID: <42780AC1.8040409@trash.net> (raw)
In-Reply-To: <20050503162550.30acf31a@dxpl.pdx.osdl.net>
Stephen Hemminger wrote:
> Fix qlen underrun when doing duplication with netem. If netem is used as
> leaf discipline, then the parent needs to be tweaked when packets are duplicated.
> + /* Since one packet can generate two packets in the
> + * queue, the parent's qlen accounting gets confused,
> + * so fix it.
> + */
> + qp = qdisc_lookup(sch->dev, TC_H_MAJ(sch->parent));
> + if (qp)
> + qp->q.qlen++;
This only works in a hierarchy with just one qdisc above netem, there
could be up to seven (check_loop_fn prevents more than that). It's also
not safe because it violates qdisc locking rules, when this code is
executed dev->queue_lock is already taken and qdisc_lookup() grabs
qdisc_tree_lock, but they can only be taken in the other order.
Regards
Patrick
next prev parent reply other threads:[~2005-05-03 23:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-03 23:25 [PATCH] (3/3) netem: adjust parent qlen when duplicating Stephen Hemminger
2005-05-03 23:24 ` David S. Miller
2005-05-03 23:35 ` Patrick McHardy [this message]
2005-05-03 23:30 ` David S. Miller
2005-05-03 23:48 ` Patrick McHardy
2005-05-03 23:59 ` David S. Miller
2005-05-04 1:54 ` Patrick McHardy
2005-05-04 1:57 ` Patrick McHardy
2005-05-04 5:01 ` Stephen Hemminger
2005-05-04 17:09 ` [RFC] alternate way of handling netem duplication Stephen Hemminger
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