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After per-node idle masks were > introduced, this path started indexing idle_cpumask() with > cpu_to_node(). > > When per-node idle tracking is disabled, per-node masks are not kept in > sync and may be stale. Reading them here can mis-detect system > utilization and lead to incorrect WAKE_SYNC wakeup placement. > > Use scx_cpu_node_if_enabled() for the waker node lookup so this check > uses the global idle mask when per-node tracking is disabled and the > per-node mask only when that mode is enabled. > > Fixes: 48849271e661 ("sched_ext: idle: Per-node idle cpumasks") > Cc: stable@vger.kernel.org # v6.15+ > Assisted-by: Codex:GPT-5 > Signed-off-by: Joseph Salisbury This is good, but it's already fixed: https://lore.kernel.org/all/20260321105503.869337-1-yphbchou0911@gmail.com You can probably use Tejun's branch to search for new issues/bugs: git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git Thanks, -Andrea > --- > kernel/sched/ext_idle.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c > index 8cfe0e9a7319..6b4520ed563d 100644 > --- a/kernel/sched/ext_idle.c > +++ b/kernel/sched/ext_idle.c > @@ -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)) && > -- > 2.47.3