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

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Message-Id: <E1Hm8Ey-0006oe-00@gondolin.me.apana.org.au>
Date:	Thu, 10 May 2007 22:59:28 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	hadi@...erus.ca
Cc:	davem@...emloft.net, herbert@...dor.apana.org.au,
	krkumar2@...ibm.com, netdev@...r.kernel.org
Subject: Re: [PATCH] sched: Optimize return value of qdisc_restart

jamal <hadi@...erus.ca> wrote:
> 
> Ok, see if this makes sense:
> 
> CPU0                 CPU1 (holding qdisc running)
>  .                    |
>  .                    |
>  .                    + grab qlock
>  .                    |
>  .                    | deq pkt
>  .                    + release qlock
>  .                    + grab txlock
>  .                    |  send pkt
>  .                    + release txlock
>  .                    + grab qlock
>   has pktX            | (NEW: qlen = 0); return 0 instead of -1
>   waiting for qlock   + release qlock

			This release qlock isn't in our source code :)

>  + grab qlock         |
>  |                    + find that return code is 0
>  | enq pkt X          + release qdisc running
>  |                    |
>  + release qlock      | ==> outta here
> 
> pkt X is stuck unless some event happens such as a new pkt arrival. 
> In other words it sits there for an indeterminate period.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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