Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test

Ryan Mallon
2011-01-24T19:56:08Z

On 01/25/2011 08:55 AM, Julia Lawall wrote:
> Function clk_get, defined just below this code, returns ERR_PTR not NULL in
> an error case.
>
> The semantic match that finds this problem is as follows:
> (http://coccinelle.lip6.fr/)
>
> // <smpl>
> @r@
> identifier f;
> @@
> f(...) { ... return ERR_PTR(...); }
>
> @@
> identifier r.f, fld;
> expression x;
> statement S1,S2;
> @@
> x = f(...)
> ... when != IS_ERR(x)
> (
> if (IS_ERR(x) ||...) S1 else S2
> |
> *x->fld
> )
> // </smpl>

I'm always really impressed by this tool :-).

>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> arch/arm/mach-at91/clock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-at91/clock.c b/arch/arm/mach-at91/clock.c
> index 9113da6..c9ee6d0 100644
> --- a/arch/arm/mach-at91/clock.c
> +++ b/arch/arm/mach-at91/clock.c
> @@ -224,7 +224,7 @@ void __init at91_clock_associate(const char *id, struct device *dev, const char
> {
> struct clk *clk = clk_get(NULL, id);
>
> - if (!dev || !clk || !IS_ERR(clk_get(dev, func)))
> + if (!dev || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
> return;

I think we want:

if (!dev || !clk || IS_ERR(clk) || !IS_ERR(clk_get(dev, func)))
return;

Since it is valid to return a NULL clk, and we don't want to try and
dereference it if that is the case.

We could also probably drop the !IS_ERR(clk_get(dev, func)) check, since
as far as I can tell it is just checking to see if the clock is already
associated, but there is no harm in re-assigning the same values, and
the two assignments in at91_clock_associate are going to be much quicker
than the lookup in clk_get.

~Ryan

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