On Tue, Mar 08, 2022 at 04:12:32PM +0100, Michal Koutný wrote: > Hello. > > On Mon, Feb 28, 2022 at 06:24:07PM +0100, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > [...] > > cpuset_attach() cpu hotplug > > --------------------------- ---------------------- > > down_write(cpuset_rwsem) > > guarantee_online_cpus() // (load cpus_attach) > > sched_cpu_deactivate > > set_cpu_active() > > // will change cpu_active_mask > > set_cpus_allowed_ptr(cpus_attach) > > __set_cpus_allowed_ptr_locked() > > // (if the intersection of cpus_attach and > > cpu_active_mask is empty, will return -EINVAL) > > up_write(cpuset_rwsem) > > [...] > > --- a/kernel/cgroup/cpuset.c > > +++ b/kernel/cgroup/cpuset.c > > @@ -1528,6 +1528,7 @@ static void cpuset_attach(struct cgroup_ > > cgroup_taskset_first(tset, &css); > > cs = css_cs(css); > > > > + cpus_read_lock(); > > mutex_lock(&cpuset_mutex); > > This backport (and possible older kernels) looks suspicious since it comes > before commit d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and > hotplug lock order") v5.4-rc1~176^2~30 when the locking order was: > cpuset lock, cpus lock. > > At the same time it also comes before commit 710da3c8ea7d ("sched/core: > Prevent race condition between cpuset and __sched_setscheduler()") > v5.4-rc1~176^2~27 when neither __sched_setscheduler() cared and this > race is similar. (The swapped locking may still conflict with > rebuild_sched_domains() before d74b27d63a8b.) Thanks for noticing this. What do you recommend to do to resolve this? thanks, greg k-h