linux-kernel - Re: [RFC PATCH 2/5] sched/core: Don't use parked cpu for selection

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aDXTOwRxhrtf5YPi@yury>
Date: Tue, 27 May 2025 10:59:07 -0400
From: Yury Norov <yury.norov@...il.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, tglx@...utronix.de, maddy@...ux.ibm.com,
	vschneid@...hat.com, dietmar.eggemann@....com, rostedt@...dmis.org,
	jstultz@...gle.com, kprateek.nayak@....com, huschle@...ux.ibm.com,
	srikar@...ux.ibm.com, linux-kernel@...r.kernel.org,
	linux@...musvillemoes.dk
Subject: Re: [RFC PATCH 2/5] sched/core: Don't use parked cpu for selection

On Fri, May 23, 2025 at 11:44:45PM +0530, Shrikanth Hegde wrote:
> When the current running task is pushed using stop class mechanism, the
> new CPU that going to be chosen shouldn't be a parked CPU. 
> 
> Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
> ---
>  kernel/sched/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 62b3416f5e43..9ec12f9b3b08 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3526,7 +3526,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
>  		nodemask = cpumask_of_node(nid);
>  
>  		/* Look for allowed, online CPU in same node. */
> -		for_each_cpu(dest_cpu, nodemask) {
> +		for_each_cpu_andnot(dest_cpu, nodemask, cpu_parked_mask) {
>  			if (is_cpu_allowed(p, dest_cpu))
>  				return dest_cpu;
>  		}
> @@ -3534,7 +3534,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
>  
>  	for (;;) {
>  		/* Any allowed, online CPU? */
> -		for_each_cpu(dest_cpu, p->cpus_ptr) {
> +		for_each_cpu_andnot(dest_cpu, p->cpus_ptr, cpu_parked_mask) {
>  			if (!is_cpu_allowed(p, dest_cpu))
>  				continue;

You test for online and dying CPUs in the is_cpu_allowed(). Why this
new 'parked' creature is different?