netdev - Re: [PATCH] fix potential wild pointer when NIC is dying

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Message-ID: <u2r412e6f7f1004140025i51e533c9t7402bc751dd925c2@mail.gmail.com>
Date:	Wed, 14 Apr 2010 15:25:01 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Tom Herbert <therbert@...gle.com>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] fix potential wild pointer when NIC is dying

On Wed, Apr 14, 2010 at 1:33 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le mercredi 14 avril 2010 à 20:18 +0800, Changli Gao a écrit :
>
> I dont see how the problem can happens, and how RPS is involved.
>
> Did you got a single panic, could you provide us a stack trace ?
>
> Maybe are you referring to NAPI ?
>
> NAPI process packets delivered by NIC, and through RPS deliver it to a
> (possibly) remote CPU queue.
>
> But at device dismantle time, we should stop NAPI on this device and
> packet delivery machinery. RPS being on or not, NAPI wont deliver new
> packets. The fact that NAPI can be throtled doesnt change the napi
> instance being disabled at this point. No more packet will be delivered
> (RPS or not)
>
> Only after this point we call flush_backlog() to make sure we dont have
> any queued packet in each cpu input_pkt_queue pointing to the device we
> dismantle.
>
> RPS doesnt change this at all.
>
> Hmm ???
>

Thanks, I got it.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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