netdev - Re: [Bugme-new] [Bug 13617] New: GRO:__napi_complete from net_rx

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Message-ID: <20090627014900.GA19639@gondor.apana.org.au>
Date:	Sat, 27 Jun 2009 09:49:00 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	dhananjay.phadke@...gic.com, akpm@...ux-foundation.org,
	bugme-daemon@...zilla.kernel.org, netdev@...r.kernel.org,
	bugzilla-daemon@...zilla.kernel.org, amit.salecha@...gic.com
Subject: Re: [Bugme-new] [Bug 13617] New: GRO:__napi_complete from
	net_rx_action crash

On Fri, Jun 26, 2009 at 10:24:58AM -0700, David Miller wrote:
>
> >>> In net_rx_action, there is check if napi_disable_pending then call
> >>> __napi_complete.
> >>> In __napi_complete, there is BUG_ON(n->gro_list);
> >>> Which has hit in below bug dump.
> >>> Why __napi_complete is called from net_rx_action instead of napi_complete.
> >>> napi_complete flushes the gro list.

Indeed, it was an oversight.  Thanks for catching it!

gro: Flush GRO packets in napi_disable_pending path

When NAPI is disabled while we're in net_rx_action, we end up
calling __napi_complete without flushing GRO packets.  This is
a bug as it would cause the GRO packets to linger, of course it
also literally BUGs to catch error like this :)

This patch changes it to napi_complete, with the obligatory IRQ
reenabling.  This should be safe because we've only just disabled
IRQs and it does not materially affect the test conditions in
between.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/net/core/dev.c b/net/core/dev.c
index 60b5728..70c27e0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2823,9 +2823,11 @@ static void net_rx_action(struct softirq_action *h)
 		 * move the instance around on the list at-will.
 		 */
 		if (unlikely(work == weight)) {
-			if (unlikely(napi_disable_pending(n)))
-				__napi_complete(n);
-			else
+			if (unlikely(napi_disable_pending(n))) {
+				local_irq_enable();
+				napi_complete(n);
+				local_irq_disable();
+			} else
 				list_move_tail(&n->poll_list, list);
 		}

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/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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