linux-kernel - RE: [GIT] Networking

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Date:	Thu, 25 Jun 2015 01:52:49 +0000
From:	"Weiny, Ira" <ira.weiny@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Doug Ledford <dledford@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"'Jason Gunthorpe (jgunthorpe@...idianresearch.com)'" 
	<jgunthorpe@...idianresearch.com>
Subject: RE: [GIT] Networking

Linus,

> 
> On the *other* side of the same conflict, I find an even more offensive commit,
> namely commit 4cd7c9479aff ("IB/mad: Add support for additional MAD info
> to/from drivers") which adds a BUG_ON() for a sanity check, rather than just
> returning -EINVAL or something sane like that.
> 
> I'm getting *real* tired of that BUG_ON() shit. I realize that infiniband is a
> niche market, and those "commercial grade" niche markets are more-than-
> used-to crap code and horrible hacks, but this is still the kernel. We don't add
> random machine-killing debug checks when it is *so* simple to just do
> 
>         if (WARN_ON_ONCE(..))
>                 return -EINVAL;
> 
> instead.

Please accept my apologies.  The original patch used WARN_ON but I was advised to use BUG_ON in a review and I should have thought about it more rather than blindly make the change.
	
> 
> Killing the machine for idiotic things like that is truly offensive, and truly
> horrible horrible code. Why do I keep on having to tell people off for doing
> these things? Why do people keep thinking that debugging-by-killing-the-
> machine is a good idea?
> 
> Either that BUG_ON() cannot possibly happen, in which case it should damn
> well not exist in the first place. Or it's a valuable debug aid, in which case it
> should damn well not be a BUG_ON. You can't have it both ways.

It was intended as a debug aid.
	
> 
> The next pointless BUG_ON() I see, I will start getting _really_ unpleasant
> about.
> 
> Doug, get rid of those things asap.

Fix submitted to Doug.

https://patchwork.kernel.org/patch/6671931/

Ira