linux-kernel - Re: WARN_ON() which sometimes sucks

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Message-ID: <18096.2592.877510.221163@cargo.ozlabs.ibm.com>
Date:	Wed, 1 Aug 2007 14:20:48 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Al Viro <viro@....linux.org.uk>, Alexey Dobriyan <adobriyan@...ru>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	herbert@...dor.apana.org.au
Subject: Re: WARN_ON() which sometimes sucks

Linus Torvalds writes:

> Umm. The WARN_ON() might actually get a "long long" value for all we know. 
> Ie it's perfectly possible that the WARN_ON might look like
> 
> 	/* Must not have high bits on */
> 	WARN_ON(offset & 0xffffffff00000000);
> 
> which on a 32-bit pcc would apparently do the wrong thing entirely as it 
> stands now. No?

Actually, because of the typeof in the powerpc WARN_ON, I think it
would fail to build since we'd be passing a long long value to an
inline asm, or at least I hope it would fail to build. :)

But your criticism is correct with regard to the powerpc BUG_ON, and
you're correct that a long wouldn't be sufficient if someone passes in
a long long.  Oh well.  I guess we just wear the extra two
instructions.

Paul.
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