[PATCH 1/2] kthread: Switch to cpu_possible_mask

From: Frederic Weisbecker
Date: Wed May 27 2020 - 10:29:20 EST

From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Chris Friesen <chris.friesen@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jim Somerville <Jim.Somerville@xxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
kernel/kthread.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index bfbfa481be3a..788bec94aca7 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -360,7 +360,7 @@ 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);
return task;
@@ -585,7 +585,7 @@ int kthreadd(void *unused)
/* Setup a clean context for our children to inherit. */
set_task_comm(tsk, "kthreadd");
- set_cpus_allowed_ptr(tsk, cpu_all_mask);
+ set_cpus_allowed_ptr(tsk, cpu_possible_mask);

current->flags |= PF_NOFREEZE;