From 60ba9c38b9316efa3eb1c8a927bee6f8a4f101a5 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 18 Jun 2025 16:52:04 +0200 Subject: [PATCH] kthread: Comment on the purpose and placement of kthread_affine_node() call It may not appear obvious why kthread_affine_node() is not called before the kthread creation completion instead of after the first wake-up. The reason is that kthread_affine_node() applies a default affinity behaviour that only takes place if no affinity preference have already been passed by the kthread creation call site. Add a comment to clarify that. Reported-by: Peter Zijlstra Signed-off-by: Frederic Weisbecker Cc: Marco Crivellari Cc: Michal Hocko Cc: Peter Zijlstra Cc: Tejun Heo Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Waiman Long --- kernel/kthread.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/kthread.c b/kernel/kthread.c index 03008154249c7..51f419139dea7 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -453,6 +453,10 @@ static int kthread(void *_create) self->started = 1; + /* + * Apply default node affinity if no call to kthread_bind[_mask]() nor + * kthread_affine_preferred() was issued before the first wake-up. + */ if (!(current->flags & PF_NO_SETAFFINITY) && !self->preferred_affinity) kthread_affine_node(); -- 2.47.3