linux-kernel - Re: kfree(0)

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Message-ID: <alpine.LFD.0.999.0708180300490.3666@enigma.security.iitk.ac.in>
Date:	Sat, 18 Aug 2007 03:02:14 +0530 (IST)
From:	Satyam Sharma <satyam@...radead.org>
To:	Christoph Lameter <clameter@....com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Tim Bird <tim.bird@...sony.com>,
	linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: kfree(0) - ok?



On Sat, 18 Aug 2007, Satyam Sharma wrote:

> On Fri, 17 Aug 2007, Christoph Lameter wrote:
> 
> > On Fri, 17 Aug 2007, Andrew Morton wrote:
> > 
> > > are we seeing a pattern here?  We could stick the unlikely inside
> > > ZERO_OR_NULL_PTR() itself.  That's a little bit sleazy though - there might
> > > be future callsites at which it is likely, who knows?
> > 
> > Thought about that myself but then there would be a weird side effect to 
> > ZERO_OR_NULL_PTR().
> 
> True, but I suspect such a side-effect to actually matter only for the
> BUG_ON case, where introducing the unlikely() would mean the output from
> the show_registers() dump during the BUG() would show a not-useful-at-all
> %%eax == 0x0000001 value, but only if CONFIG_PROFILE_LIKELY=y, admittedly.

Hang on, BUG_ON() already uses unlikely anyway. And I've just verified
from a testcase that gcc doesn't get confused by unlikely(unlikely(...))
kind of code, so we're in the clear, I think.
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