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 <[email protected]> --- init/main.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/init/main.c +++ b/init/main.c @@ -389,6 +389,7 @@ static __initdata DECLARE_COMPLETION(kth static noinline void __ref rest_init(void) { + struct task_struct *tsk; int pid; rcu_scheduler_starting(); @@ -397,7 +398,17 @@ static noinline void __ref rest_init(voi * the init task will end up wanting to create kthreads, which, if * we schedule it before we create kthreadd, will OOPS. */ - kernel_thread(kernel_init, NULL, CLONE_FS); + pid = kernel_thread(kernel_init, NULL, CLONE_FS); + /* + * 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. + */ + rcu_read_lock(); + tsk = find_task_by_pid_ns(pid, &init_pid_ns); + set_cpus_allowed_ptr(tsk, cpumask_of(smp_processor_id())); + rcu_read_unlock(); + numa_default_policy(); pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES); rcu_read_lock(); @@ -1015,10 +1026,6 @@ 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. - */ - set_cpus_allowed_ptr(current, cpu_all_mask); cad_pid = task_pid(current);
