netdev - Re: [PATCH] sched: Optimize return value of qdisc

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Message-Id: <20070510.045534.90119358.davem@davemloft.net>
Date:	Thu, 10 May 2007 04:55:34 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	krkumar2@...ibm.com, hadi@...erus.ca, netdev@...r.kernel.org
Subject: Re: [PATCH] sched: Optimize return value of qdisc_restart

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Thu, 10 May 2007 21:50:39 +1000

> On Thu, May 10, 2007 at 10:42:59AM +0530, Krishna Kumar2 wrote:
> > 
> > But RUNNING is never relinquished till all the way back out to
> > __qdisc_run. Only the lock is dropped before calling xmit and
> > re-got after xmit is finished (all the while holding RUNNING).
> > After xmit both queue_lock and RUNNING are held. If some other
> > cpu enqueue'd during this release window (and they would have
> > returned after dropping the lock as they are pure enqueuer's),
> > qdisc_restart will find those skbs. Similarly if no skbs were
> > added, qdisc_restart will return 0.
> 
> Yes I agree with Krishna completely.  In fact this whole section
> is so 20th-century :) Let's fix up the comments too while we're
> at it.
> 
> [NET_SCHED]: Rationalise return value of qdisc_restart
> 
> The current return value scheme and associated comment was invented
> back in the 20th century when we still had that tbusy flag.  Things
> have changed quite a bit since then (even Tony Blair is moving on
> now, not to mention the new French president).
> 
> All we need to indicate now is whether the caller should continue
> processing the queue.  Therefore it's sufficient if we return 0 if
> we want to stop and non-zero otherwise.
> 
> This is based on a patch by Krishna Kumar.
> 
> Signed-off-by: <herbert@...dor.apana.org.au>

Fair enough, patch applied :-)
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