netdev - Re: sungem triggers NAPI warning

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Date:	Sun, 23 Mar 2008 03:35:58 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	johannes@...solutions.net
Cc:	netdev@...r.kernel.org, benh@...nel.crashing.org
Subject: Re: sungem triggers NAPI warning

From: Johannes Berg <johannes@...solutions.net>
Date: Tue, 19 Feb 2008 22:38:43 +0100

> In order to trigger it, I have to transfer a lot of data. I have
> triggered it now with a full kernel recompilation using -j6 and distcc
> onto a fast machine (with tg3 network, direct cable, gbit), and with
> rsync transferring 26GiB data between the machines.

I'll push the following fix.

Ben, thanks for letting this fall through the cracks :-)

commit da990a2402aeaee84837f29054c4628eb02f7493
Author: David S. Miller <davem@...emloft.net>
Date:   Sun Mar 23 03:35:12 2008 -0700

    [SUNGEM]: Fix NAPI assertion failure.
    
    As reported by Johannes Berg:
    
    I started getting this warning with recent kernels:
    
    [  773.908927] ------------[ cut here ]------------
    [  773.908954] Badness at net/core/dev.c:2204
     ...
    
    If we loop more than once in gem_poll(), we'll
    use more than the real budget in our gem_rx()
    calls, thus eventually trigger the caller's
    assertions in net_rx_action().
    
    Subtract "work_done" from "budget" for the second
    arg to gem_rx() to fix the bug.
    
    Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/drivers/net/sungem.c b/drivers/net/sungem.c
index 9721279..4291458 100644
--- a/drivers/net/sungem.c
+++ b/drivers/net/sungem.c
@@ -912,7 +912,7 @@ static int gem_poll(struct napi_struct *napi, int budget)
 		 * rx ring - must call napi_disable(), which
 		 * schedule_timeout()'s if polling is already disabled.
 		 */
-		work_done += gem_rx(gp, budget);
+		work_done += gem_rx(gp, budget - work_done);
 
 		if (work_done >= budget)
 			return work_done;
--
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