linux-kernel - Re: [PATCH 3/8] drivers/pcmcia: remove unnecessary kzalloc

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Date:	Sat, 21 Nov 2009 16:12:59 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	walter harms <wharms@....de>
Cc:	linux-pcmcia@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, rmk+kernel@....linux.org.uk,
	linux@....linux.org.uk
Subject: Re: [PATCH 3/8] drivers/pcmcia: remove unnecessary kzalloc

On Sat, 21 Nov 2009, walter harms wrote:

> 
> 
> Julia Lawall schrieb:
> > From: Julia Lawall <julia@...u.dk>
> > 
> > The result of calling kzalloc is never used or freed.
> > 
> > The semantic match that finds this problem is as follows:
> > (http://www.emn.fr/x-info/coccinelle/)
> > 
> > // <smpl>
> > @r exists@
> > local idexpression x;
> > statement S;
> > expression E;
> > identifier f,f1,l;
> > position p1,p2;
> > expression *ptr != NULL;
> > @@
> > 
> > x@p1 = \(kmalloc\|kzalloc\|kcalloc\)(...);
> > ...
> > if (x == NULL) S
> > <... when != x
> >      when != if (...) { <+...x...+> }
> > (
> > x->f1 = E
> > |
> >  (x->f1 == NULL || ...)
> > |
> >  f(...,x->f1,...)
> > )
> > ...>
> > (
> >  return \(0\|<+...x...+>\|ptr\);
> > |
> >  return@p2 ...;
> > )
> > 
> > @script:python@
> > p1 << r.p1;
> > p2 << r.p2;
> > @@
> > 
> > print "* file: %s kmalloc %s return %s" % (p1[0].file,p1[0].line,p2[0].line)
> > // </smpl>
> > 
> > Signed-off-by: Julia Lawall <julia@...u.dk>
> > ---
> >  drivers/pcmcia/sa1111_generic.c     |    4 ----
> >  1 files changed, 0 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pcmcia/sa1111_generic.c b/drivers/pcmcia/sa1111_generic.c
> > index deb5036..de6bc33 100644
> > --- a/drivers/pcmcia/sa1111_generic.c
> > +++ b/drivers/pcmcia/sa1111_generic.c
> > @@ -127,10 +127,6 @@ int sa1111_pcmcia_add(struct sa1111_dev *dev, struct pcmcia_low_level *ops,
> >  	ops->socket_state = sa1111_pcmcia_socket_state;
> >  	ops->socket_suspend = sa1111_pcmcia_socket_suspend;
> >  
> > -	s = kzalloc(sizeof(*s) * ops->nr, GFP_KERNEL);
> > -	if (!s)
> > -		return -ENODEV;
> > -
> >  	for (i = 0; i < ops->nr; i++) {
> >  		s = kzalloc(sizeof(*s), GFP_KERNEL);
> >  		if (!s)
> 
> 
> 
> mmmh, perhaps the original idea was to have an array
> and then he moved to a linked list ?
> 
> I thing the array idea is better (1. it fails on low mem propperly, 2. no need free()
> 3. less zmalloc stuff) but requieres that pcmcia_remove()
> will release that array propperly
> 
> the bug is strange,

Both kzallocs were added at the same time, when the function was added in 
commit 701a5dc05ad99a06958b3f97cb69d99b47cebee3.  I have added the author 
to the CC list.

julia
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