From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexey Dobriyan <adobriyan@gmail.com>
Subject: Re: [PATCH v3 01/21] grace: replace BUG_ON by WARN_ONCE in exit_net
 hook
Date: Tue, 7 Nov 2017 15:26:17 +0300
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> -	BUG_ON(!list_empty(grace_list));
> +	WARN_ONCE(!list_empty(grace_list),
> +		  "net %x %s: grace_list is not empty\n",
> +		  net->ns.inum, __func__);

* printing __func__ is unnecessary as it will be on top of the stacktrace anyway,
* message duplicates condition
* printing netns id in netns ->exit hook also looks like pointless
  information: for kernel dumps you want struct net pointer right away.
  You wrote admins want to know which container triggered the message
  but what will they do with that information?


I'd say WARN_ONCE(!list_empty()) is enough.
BUG_ON if you ship with crashdumps by default.