linux-kernel - Re: [PATCH] Fix WARN_ON / WARN_ON

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Date:	Sat, 07 Oct 2006 17:39:18 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Andrew Morton <akpm@...l.org>,
	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>,
	tim.c.chen@...ux.intel.com, herbert@...dor.apana.org.au,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix WARN_ON / WARN_ON_ONCE regression

Steven Rostedt wrote:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=114935833125957&w=2
>
> That was different, since we were putting a likely condition in an
> unlikely(). But I still don't see why we would ever want to test
> __warn_once before the condition, since it doesn't save on anything and
> just adds extra work.  I don't see the savings.
>   

Also, in that thread you cite (__warn_once && (condition)) is flat-out 
wrong, because condition may have a side-effect.  There are plenty of 
places in the code which use BUG_ON or WARN_ON as a general error 
checking mechanism which expect the condition to be always evaluated 
once; WARN_ON_ONCE should be the same.

Personally I think it is poor style, but there you are.

    J
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