linux-kernel - Re: [PATCH v1] ath5k: fix WARNING opportunity for swap.

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Date:   Mon, 14 Aug 2023 15:31:03 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Mahmoud Maatuq <mahmoudmatook.mm@...il.com>,
        <jirislaby@...nel.org>, <mickflemm@...il.com>, <mcgrof@...nel.org>,
        <kvalo@...nel.org>, <linux-wireless@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <linux-kernel-mentees@...ts.linuxfoundation.org>
Subject: Re: [PATCH v1] ath5k: fix WARNING opportunity for swap.

On 8/14/2023 3:28 PM, Jeff Johnson wrote:
> On 8/14/2023 1:02 PM, Mahmoud Maatuq wrote:
>> coccinielle reported the following:
>> ./drivers/net/wireless/ath/ath5k/phy.c:1573:25-26: WARNING opportunity 
>> for swap()
> 
> Suggest you add something like:
> 
> This revealed that ath5k_hw_get_median_noise_floor() had open-coded 
> sort() functionality. Since ath5k_hw_get_median_noise_floor() only 
> executes once every 10 seconds, any extra overhead due to sort() calling 
> it's "compare" and "swap" functions can be ignored, so replace the 

<blush> and of course that should be its and not it's </blush>

> existing logic with a call to sort().
> 
> and before your SOB add:
> Suggested-by: Jiri Slaby <jirislaby@...nel.org>
> 
>> Signed-off-by: Mahmoud Maatuq <mahmoudmatook.mm@...il.com>
>> ---
>> changes in v1:
>> - replace the entire double loop with sort()
>>    as suggested by Jiri Slaby <jirislaby@...nel.org>
>> ---
>>   drivers/net/wireless/ath/ath5k/phy.c | 29 +++++++++++++---------------
>>   1 file changed, 13 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/net/wireless/ath/ath5k/phy.c 
>> b/drivers/net/wireless/ath/ath5k/phy.c
>> index 5797ef9c73d7..7ee4e1616f45 100644
>> --- a/drivers/net/wireless/ath/ath5k/phy.c
>> +++ b/drivers/net/wireless/ath/ath5k/phy.c
>> @@ -26,6 +26,7 @@
>>   #include <linux/delay.h>
>>   #include <linux/slab.h>
>> +#include <linux/sort.h>
>>   #include <asm/unaligned.h>
>>   #include "ath5k.h"
>> @@ -1554,6 +1555,11 @@ static void ath5k_hw_update_nfcal_hist(struct 
>> ath5k_hw *ah, s16 noise_floor)
>>       hist->nfval[hist->index] = noise_floor;
>>   }
>> +static int cmps16(const void *a, const void *b)
>> +{
>> +    return *(s16 *)a - *(s16 *)b;
>> +}
>> +
>>   /**
>>    * ath5k_hw_get_median_noise_floor() - Get median NF from history 
>> buffer
>>    * @ah: The &struct ath5k_hw
>> @@ -1561,25 +1567,16 @@ static void ath5k_hw_update_nfcal_hist(struct 
>> ath5k_hw *ah, s16 noise_floor)
>>   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;
>> -            }
>> -        }
>> -    }
>> +    s16 sorted_nfval[ATH5K_NF_CAL_HIST_MAX];
>> +    int i;
>> +
>> +    memcpy(sorted_nfval, ah->ah_nfcal_hist.nfval, sizeof(sorted_nfval));
>> +    sort(sorted_nfval, ATH5K_NF_CAL_HIST_MAX, sizeof(s16), cmps16, 
>> NULL);
>>       for (i = 0; i < ATH5K_NF_CAL_HIST_MAX; i++) {
>>           ATH5K_DBG(ah, ATH5K_DEBUG_CALIBRATE,
>> -            "cal %d:%d\n", i, sort[i]);
>> +            "cal %d:%d\n", i, sorted_nfval[i]);
>>       }
>> -    return sort[(ATH5K_NF_CAL_HIST_MAX - 1) / 2];
>> +    return sorted_nfval[(ATH5K_NF_CAL_HIST_MAX - 1) / 2];
>>   }
>>   /**
>