Re: [PATCH 1/6] net: ip4_datagram_connect: Use correct form ofstatistics update

From: Peter Zijlstra
Date: Wed Oct 16 2013 - 04:36:12 EST


On Tue, Oct 15, 2013 at 12:47:23PM -0500, Christoph Lameter wrote:
> ip4_datagram_connect is called with BH processing enabled. Therefore
> we cannot use IP_INC_STATS_BH but must use IP_INC_STATS which disables
> BH handling before incrementing the counter.
>
> The following trace is triggered without this patch:
>
> [ 9293.806634] __this_cpu_add operation in preemptible [00000000] code: ntpd/2150

You lost the BUG there; that really needs to be there:

- BUG makes people pay attention
- This was an actual BUG wasn't it?

Sure there can be false positives, but in all cases people should amend
the code. Sometimes with a comment explaining why the raw primitive
should be used; sometimes to fix an actual bug, but a patch needs to be
written. Therefore BUG!
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