linux-kernel - Re: [PATCH] ath5k: fix WARNING opportunity for swap.

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Date:   Tue, 8 Aug 2023 23:42:58 +0400
From:   Mahmoud Matook <mahmoudmatook.mm@...il.com>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     mickflemm@...il.com, mcgrof@...nel.org, kvalo@...nel.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        mahmoudmatook.mm@...il.com
Subject: Re: [PATCH] ath5k: fix WARNING opportunity for swap.

On 08/08, Jiri Slaby wrote:

> On 07. 08. 23, 22:10, Mahmoud Maatuq wrote:
> > coccinielle reported the following:
> > ./drivers/net/wireless/ath/ath5k/phy.c:1573:25-26: WARNING opportunity for swap()
> 
> 
> OK, once again:
> https://lore.kernel.org/all/0c3acbd4-6ab2-5cc5-6293-54e30093cce2@kernel.org/


I had a look at the commit history, to see why the original developer 
didn't use sort() function, and name the array variable sort but found
nothing. 
I have some doubts that he might did that intentionally, so not to call
sort() function for such small array and avoid the cost of context
switching.


> > Signed-off-by: Mahmoud Maatuq <mahmoudmatook.mm@...il.com>
> > ---
> >   drivers/net/wireless/ath/ath5k/phy.c | 5 +----
> >   1 file changed, 1 insertion(+), 4 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/ath/ath5k/phy.c b/drivers/net/wireless/ath/ath5k/phy.c
> > index 5797ef9c73d7..f87eb684f223 100644
> > --- a/drivers/net/wireless/ath/ath5k/phy.c
> > +++ b/drivers/net/wireless/ath/ath5k/phy.c
> > @@ -1562,16 +1562,13 @@ static s16
> >   ath5k_hw_get_median_noise_floor(struct ath5k_hw *ah)
> >   {
> >   	s16 sort[ATH5K_NF_CAL_HIST_MAX];
> > -	s16 tmp;
> >   	int i, j;
> >   	memcpy(sort, ah->ah_nfcal_hist.nfval, sizeof(sort));
> >   	for (i = 0; i < ATH5K_NF_CAL_HIST_MAX - 1; i++) {
> >   		for (j = 1; j < ATH5K_NF_CAL_HIST_MAX - i; j++) {
> >   			if (sort[j] > sort[j - 1]) {
> > -				tmp = sort[j];
> > -				sort[j] = sort[j - 1];
> > -				sort[j - 1] = tmp;
> > +				swap(sort[j], sort[j - 1]);
> >   			}
> >   		}
> >   	}
> 
> -- 
> js
> suse labs