On Sun, 14 May 2017 20:27:17 +0200 Thomas Gleixner <t...@linutronix.de> wrote:
> 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 <t...@linutronix.de> Reviewed-by: Steven Rostedt (VMware) <rost...@goodmis.org> -- Steve > --- > 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); > >
