kthread: Switch to cpu_possible_mask

Next patch will switch unbound kernel threads mask to
housekeeping_cpumask(), a subset of cpu_possible_mask. So in order to
ease bisection, lets first switch kthreads default affinity from
cpu_all_mask to cpu_possible_mask.

It looks safe to do so as cpu_possible_mask seem to be initialized
at setup_arch() time, way before kthreadd is created.

Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200527142909.23372-2-frederic@kernel.org

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 8e3d2d7fdf5e296994b2902e97b28d44a8c9d09e..b86d37cda10928050eb36a60a2cf83e033533de3 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -383,7 +383,7 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
                 * The kernel thread should not inherit these properties.
                 */
                sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
-               set_cpus_allowed_ptr(task, cpu_all_mask);
+               set_cpus_allowed_ptr(task, cpu_possible_mask);
        }
        kfree(create);
        return task;
@@ -608,7 +608,7 @@ int kthreadd(void *unused)
        /* Setup a clean context for our children to inherit. */
        set_task_comm(tsk, "kthreadd");
        ignore_signals(tsk);
-       set_cpus_allowed_ptr(tsk, cpu_all_mask);
+       set_cpus_allowed_ptr(tsk, cpu_possible_mask);
        set_mems_allowed(node_states[N_MEMORY]);
 
        current->flags |= PF_NOFREEZE;