[PATCH -next] locking/ww_mutex: use swap() in get_random_order()

[PATCH -next] locking/ww_mutex: use swap() in get_random_order()

[Jiapeng Chong]

Use existing swap() function rather than duplicating its implementation.

./kernel/locking/test-ww_mutex.c:420:22-23: WARNING opportunity for swap().

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=11531
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
 kernel/locking/test-ww_mutex.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 5d58b2c0ef98..bcb1b9fea588 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -404,7 +404,7 @@ static inline u32 prandom_u32_below(u32 ceil)
 static int *get_random_order(int count)
 {
 	int *order;
-	int n, r, tmp;
+	int n, r;
 
 	order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
 	if (!order)
@@ -415,11 +415,8 @@ static int *get_random_order(int count)
 
 	for (n = count - 1; n > 1; n--) {
 		r = prandom_u32_below(n + 1);
-		if (r != n) {
-			tmp = order[n];
-			order[n] = order[r];
-			order[r] = tmp;
-		}
+		if (r != n)
+			swap(order[n], order[r]);
 	}
 
 	return order;
-- 
2.32.0.3.g01195cf9f

Re: [PATCH -next] locking/ww_mutex: use swap() in get_random_order()

[Boqun Feng]

On Fri, Oct 25, 2024 at 04:14:55PM +0800, Jiapeng Chong wrote:
> Use existing swap() function rather than duplicating its implementation.
> 
> ./kernel/locking/test-ww_mutex.c:420:22-23: WARNING opportunity for swap().
> 
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=11531
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

Thanks for the patch. However, I think Thorsten Blum beat you to it [1].
Would it be Ok if I queue that patch with you as a Reported-by (plus
the other Reported-by tag and Close tag)?

[1]: https://lore.kernel.org/r/20240731135850.81018-2-thorsten.blum@toblux.com

Regards,
Boqun

> ---
>  kernel/locking/test-ww_mutex.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
> index 5d58b2c0ef98..bcb1b9fea588 100644
> --- a/kernel/locking/test-ww_mutex.c
> +++ b/kernel/locking/test-ww_mutex.c
> @@ -404,7 +404,7 @@ static inline u32 prandom_u32_below(u32 ceil)
>  static int *get_random_order(int count)
>  {
>  	int *order;
> -	int n, r, tmp;
> +	int n, r;
>  
>  	order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
>  	if (!order)
> @@ -415,11 +415,8 @@ static int *get_random_order(int count)
>  
>  	for (n = count - 1; n > 1; n--) {
>  		r = prandom_u32_below(n + 1);
> -		if (r != n) {
> -			tmp = order[n];
> -			order[n] = order[r];
> -			order[r] = tmp;
> -		}
> +		if (r != n)
> +			swap(order[n], order[r]);
>  	}
>  
>  	return order;
> -- 
> 2.32.0.3.g01195cf9f
>