Commit db08b194 authored by Cheng-Yang Chou's avatar Cheng-Yang Chou Committed by Tejun Heo
Browse files

sched_ext: Fix inconsistent NUMA node lookup in scx_select_cpu_dfl() 



In the WAKE_SYNC path of scx_select_cpu_dfl(), waker_node was computed
with cpu_to_node(), while node (for prev_cpu) was computed with
scx_cpu_node_if_enabled(). When scx_builtin_idle_per_node is disabled,
idle_cpumask(waker_node) is called with a real node ID even though
per-node idle tracking is disabled, resulting in undefined behavior.

Fix by using scx_cpu_node_if_enabled() for waker_node as well, ensuring
both variables are computed consistently.

Fixes: 48849271 ("sched_ext: idle: Per-node idle cpumasks")
Cc: stable@vger.kernel.org # v6.15+
Signed-off-by: default avatarCheng-Yang Chou <yphbchou0911@gmail.com>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 2fcfe595

kernel/sched/ext_idle.c

+1 −1
Original line number Diff line number Diff line
@@ -543,7 +543,7 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, 
		 * piled up on it even if there is an idle core elsewhere on

		 * the system.

		 */

		waker_node = cpu_to_node(cpu);

		waker_node = scx_cpu_node_if_enabled(cpu);

		if (!(current->flags & PF_EXITING) &&

		    cpu_rq(cpu)->scx.local_dsq.nr == 0 &&

		    (!(flags & SCX_PICK_IDLE_IN_NODE) || (waker_node == node)) &&