linux-kernel - Re: [PATCH] cgroup/cpuset: Adjust exception handling in generate_sched

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Date: Wed, 10 Jan 2024 10:21:45 -0500
From: Waiman Long <longman@...hat.com>
To: Markus Elfring <Markus.Elfring@....de>, cgroups@...r.kernel.org,
 kernel-janitors@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
 Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cgroup/cpuset: Adjust exception handling in
 generate_sched_domains()

On 12/31/23 02:28, Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Sun, 31 Dec 2023 08:00:31 +0100
>
> Two resource allocation failures triggered further actions
> over the label “done” so far.
>
> * Jump to the statement “ndoms = 1;” in three cases directly
>    by using the label “set_ndoms” instead.
>
> * Delete an assignment for the variable “ndoms” in one if branch.
>
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>   kernel/cgroup/cpuset.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index ba36c073304a..29ccd52eb45c 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -973,10 +973,9 @@ static int generate_sched_domains(cpumask_var_t **domains,
>
>   	/* Special case for the 99% of systems with one, full, sched domain */
>   	if (root_load_balance && !top_cpuset.nr_subparts) {
> -		ndoms = 1;

This statement cannot be removed as it is used in the following 
statement to size the allocation. This change the behavior to make doms 
NULL rather than a 1-entry array. This is probably the cause of the 
kernel test robot failure report.

NAK

>   		doms = alloc_sched_domains(ndoms);
>   		if (!doms)
> -			goto done;
> +			goto set_ndoms;
>
>   		dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
>   		if (dattr) {
> @@ -986,12 +985,12 @@ static int generate_sched_domains(cpumask_var_t **domains,
>   		cpumask_and(doms[0], top_cpuset.effective_cpus,
>   			    housekeeping_cpumask(HK_TYPE_DOMAIN));
>
> -		goto done;
> +		goto set_ndoms;
>   	}
>
>   	csa = kmalloc_array(nr_cpusets(), sizeof(cp), GFP_KERNEL);
>   	if (!csa)
> -		goto done;
> +		goto set_ndoms;
>   	csn = 0;
>
>   	rcu_read_lock();
> @@ -1123,6 +1122,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
>   	 * See comments in partition_sched_domains().
>   	 */
>   	if (doms == NULL)
> +set_ndoms:
>   		ndoms = 1;
>
>   	*domains    = doms;
> --
> 2.43.0
>
>