linux-kernel - Re: [PATCH] Allow NULL pointers in percpu

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Message-Id: <1163787247.3097.14.camel@localhost.localdomain>
Date:	Fri, 17 Nov 2006 10:14:07 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Andrew Morton <akpm@...l.org>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Lameter <clameter@....com>,
	Pedro Roque <roque@...fc.ul.pt>,
	"David S. Miller" <davem@...emloft.net>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Allow NULL pointers in percpu_free

On Fri, 2006-11-17 at 13:07 -0500, Alan Stern wrote:
> On Fri, 17 Nov 2006, Daniel Walker wrote:
> 
> > On Fri, 2006-11-17 at 12:36 -0500, Alan Stern wrote:
> > 
> > >  void percpu_free(void *__pdata)
> > >  {
> > > +	if (!__pdata)
> > > +		return;
> > 
> > Should be unlikely() right?
> 
> It certainly could be.  I tend not to put such annotations in my code, but 
> it wouldn't hurt.

It's actually a really good idea to add them .. I've noticed they tend
to make my kernels smaller, although I wouldn't expect that to always be
the case.. Another reason is that in -mm we can track how often this
condition is triggered with likely profiling. With kfree, for instance,
there were a number of callers that frequently called kfree(NULL), which
IMO isn't good.

Daniel

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