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

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Message-ID: <20230812045701.erg57tzebp4nebpo@mmaatuq-HP-Laptop-15-dy2xxx>
Date:   Sat, 12 Aug 2023 08:57:01 +0400
From:   Mahmoud Matook <mahmoudmatook.mm@...il.com>
To:     Jiri Slaby <jirislaby@...nel.org>, 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. 23, 21:42, Mahmoud Matook wrote:
>> 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

> It happens once in 10 s and in a work. No worries about that.

if it's the case so make sense to use sort().
but should I send the modifications on the same thread?
as the subject needs to be changed.
ex: repalce double loop with sort function
    replace bubble sort with heap sort. 

>> and avoid the cost of context switching.

> What context switching?

I used the wrong expression, I meant function call overhead 
e.g store/load registers.

>>>> 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
>
> -- 
> js
> suse labs