linux-kernel - Re: [PATCH next] cgroup/cpuset: Cleanup signedness issue in cpu_exclusive

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Date:   Wed, 27 Sep 2023 09:13:49 -0400
From:   Waiman Long <longman@...hat.com>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        Zefan Li <lizefan.x@...edance.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com, kamalesh.babulal@...cle.com,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH next] cgroup/cpuset: Cleanup signedness issue in
 cpu_exclusive_check()

On 9/27/23 02:58, Harshit Mogalapalli wrote:
> Smatch complains about returning negative error codes from a type
> bool function.
>
> kernel/cgroup/cpuset.c:705 cpu_exclusive_check() warn:
> 	signedness bug returning '(-22)'
>
> The code works correctly, but it is confusing.  The current behavior is
> that cpu_exclusive_check() returns true if it's *NOT* exclusive.  Rename
> it to cpusets_are_exclusive() and reverse the returns so it returns true
> if it is exclusive and false if it's not.  Update both callers as well.
>
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <error27@...il.com>
> Closes: https://lore.kernel.org/r/202309201706.2LhKdM6o-lkp@intel.com/
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> ---
> This is based on sattic analysis, only compile tested
> ---
>   kernel/cgroup/cpuset.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 15f399153a2e..afefddd33c3e 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -719,18 +719,18 @@ static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
>   }
>   
>   /*
> - * cpu_exclusive_check() - check if two cpusets are exclusive
> + * cpusets_are_exclusive() - check if two cpusets are exclusive
>    *
> - * Return 0 if exclusive, -EINVAL if not
> + * Return true if exclusive, false if not
>    */
> -static inline bool cpu_exclusive_check(struct cpuset *cs1, struct cpuset *cs2)
> +static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>   {
>   	struct cpumask *xcpus1 = fetch_xcpus(cs1);
>   	struct cpumask *xcpus2 = fetch_xcpus(cs2);
>   
>   	if (cpumask_intersects(xcpus1, xcpus2))
> -		return -EINVAL;
> -	return 0;
> +		return false;
> +	return true;
>   }
>   
>   /*
> @@ -833,7 +833,7 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
>   	cpuset_for_each_child(c, css, par) {
>   		if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
>   		    c != cur) {
> -			if (cpu_exclusive_check(trial, c))
> +			if (!cpusets_are_exclusive(trial, c))
>   				goto out;
>   		}
>   		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
> @@ -1864,7 +1864,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   			cpuset_for_each_child(child, css, parent) {
>   				if (child == cs)
>   					continue;
> -				if (cpu_exclusive_check(cs, child)) {
> +				if (!cpusets_are_exclusive(cs, child)) {
>   					exclusive = false;
>   					break;
>   				}

Thanks for fixing that.

Acked-by: Waiman Long <longman@...hat.com>