Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: Question about a8ea6fc9b089 ("sched: Stop PF_NO_SETAFFINITY from being inherited by various init system threads") | Date | Thu, 10 Jun 2021 19:28:57 +0100 |
| |
On 10/06/21 10:04, Paul E. McKenney wrote:
Hi, > Hello, Frederic, > > This commit works well, but has the unfortunate side-effect of making > smp_processor_id() complain when used in a preemptible region even > though the kthread has been pinned onto a single CPU by a call to > set_cpus_allowed_ptr(). (Which did return success.) >
On which tree are you encountering this?
Looking at check_preemption_disabled() and CPU affinity, v5.13-rc5 has:
/* * Kernel threads bound to a single CPU can safely use * smp_processor_id(): */ if (current->nr_cpus_allowed == 1) goto out;
tip/sched/core additionally hinges that on PF_NO_SETAFFINITY:
570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed")
The former shouldn't be affected by Frederic's patch, and the latter should only cause warnings if the pinned task isn't a "proper" kthread (thus doesn't have PF_NO_SETAFFINITY)... Exceptions that come to mind are things like UMH which doesn't use kthread_create().
> This isn't a big deal -- I can easily switch to raw_smp_processor_id(), > which is arguably a better choice anyway because it prevents the > complaints from flooding out any real warnings due to error returns > from set_cpus_allowed_ptr() or something else unpinning the kthread. > Which I am in the process of doing: > > 516e52e9f5ec ("scftorture: Avoid excess warnings") > 475d6d49f21d ("refscale: Avoid excess warnings in ref_scale_reader()") > > But I figured that I should check to see if this change was in fact > intentional. > > Thanx, Paul
| |