linux-kernel - Re: [PATCH] Make WARN_ON/WARN_ON_ONCE no-ops when CONFIG

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Message-ID: <20071215060449.GA26199@gondor.apana.org.au>
Date:	Sat, 15 Dec 2007 14:04:49 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH] Make WARN_ON/WARN_ON_ONCE no-ops when CONFIG_BUG is off

On Fri, Dec 14, 2007 at 11:52:18PM -0600, Matt Mackall wrote:
>
> No. The code as written above should reduce to:
> 
> 	if (val == NULL)
> 		return -EFAULT;
> 
> If I hadn't wanted to return -EFAULT in this case, I would have just written:
> 
> 	WARN_ON(val == NULL);

Well the only reason I introduced

	if (WARN_ON)

is so that what would otherwise be a BUG_ON condition would have
a chance to get written to disk when invoked from an IRQ handler.

> I don't want code that was running safely (ie returning -EFAULT) to
> start crashing the system just because I've, say, disabled printk.
> That's creating an obnoxious heisenbug.

I'm disappointed that it has been used in ways that it shouldn't
have been.

I suppose we'll have to either introduce a new primitive or just
go back to using BUG_ON.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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