Re: [PATCH-next v2 1/2] sched/isolation: Make HK_TYPE_KTHREAD an alias of HK_TYPE_DOMAIN

[Frederic Weisbecker <frederic@kernel.org>]

Le Tue, Mar 31, 2026 at 12:50:14PM -0400, Waiman Long a écrit :
> Since commit 041ee6f3727a ("kthread: Rely on HK_TYPE_DOMAIN for preferred
> affinity management"), kthreads default to use the HK_TYPE_DOMAIN
> cpumask. IOW, it is no longer affected by the setting of the nohz_full
> boot kernel parameter.
> 
> That means HK_TYPE_KTHREAD should now be an alias of HK_TYPE_DOMAIN
> instead of HK_TYPE_KERNEL_NOISE to correctly reflect the current kthread
> behavior. Make the change as HK_TYPE_KTHREAD is still being used in
> some networking code.
> 
> Fixes: 041ee6f3727a ("kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management")
> Signed-off-by: Waiman Long <longman@redhat.com>

This makes ipvs_proc_est_cpumask_get() racy because now without RCU locked the
mask pointer can be released at any point.

Other users:

sysctl_est_cpulist() -> ip_vs_est_stopped_recalc() -> ip_vs_est_reload_start()

Here sysctl_est_cpulist() is only invoked if ->est_cpulist_valid
(->est_mutex makes it stable). So housekeeping_cpumask() should not be called.

But ip_vs_est_max_threads() is more complicated. And it's a sign we should
probably call something like ipvs_proc_est_cpumask_set() when the HK_TYPE_DOMAIN
is modified (and ipvs->est_cpulist_valid is 0) in order to update the ipvs
kthreads accordingly.

Thanks.

-- 
Frederic Weisbecker
SUSE Labs