Some of the boot code in init_kernel_freeable() which runs before SMP bringup assumes (rightfully) that it runs on the boot cpu and therefor can use smp_processor_id() in preemptible context. That works so far because the smp_processor_id() check starts to be effective after smp bringup. That's just wrong. Starting with SMP bringup and the ability to move threads around, smp_processor_id() in preemptible context is broken. Aside of that it does not make sense to allow init to run on all cpus before sched_smp_init() has been run. Pin the init to the boot cpu so the existing code can continue to use smp_processor_id() without triggering the checks when the enabling of those checks starts earlier. Signed-off-by: Thomas Gleixner --- init/main.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/init/main.c +++ b/init/main.c @@ -1015,10 +1015,13 @@ static noinline void __init kernel_init_ * init can allocate pages on any node */ set_mems_allowed(node_states[N_MEMORY]); + /* - * init can run on any cpu. + * Pin init on the boot cpu. Task migration is not properly working + * until sched_init_smp() has been run. It will set the allowed + * cpus for init to the non isolated cpus. */ - set_cpus_allowed_ptr(current, cpu_all_mask); + set_cpus_allowed_ptr(current, cpumask_of(raw_smp_processor_id())); cad_pid = task_pid(current);