[PATCH] sched_ext: Use the resched_cpu() to replace resched_curr() in the bypass_lb_node()
From: Zqiang
Date: Mon Dec 22 2025 - 06:53:51 EST
For the PREEMPT_RT kernels, the scx_bypass_lb_timerfn() running in the
preemptible per-CPU ktimer kthread context, this means that the following
scenarios will occur(for x86 platform):
cpu1 cpu2
ktimer kthread:
->scx_bypass_lb_timerfn
->bypass_lb_node
->for_each_cpu(cpu, resched_mask)
migration/1: by preempt by migration/2:
multi_cpu_stop() multi_cpu_stop()
->take_cpu_down()
->__cpu_disable()
->set cpu1 offline
->rq1 = cpu_rq(cpu1)
->resched_curr(rq1)
->smp_send_reschedule(cpu1)
->native_smp_send_reschedule(cpu1)
->if(unlikely(cpu_is_offline(cpu))) {
WARN(1, "sched: Unexpected
reschedule of offline CPU#%d!\n", cpu);
return;
}
This commit therefore use the resched_cpu() to replace resched_curr()
in the bypass_lb_node() to avoid send-ipi to offline CPUs.
Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxx>
---
kernel/sched/ext.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 5ebf8a740847..8f6d8d7f895c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3956,13 +3956,8 @@ static void bypass_lb_node(struct scx_sched *sch, int node)
nr_donor_target, nr_target);
}
- for_each_cpu(cpu, resched_mask) {
- struct rq *rq = cpu_rq(cpu);
-
- raw_spin_rq_lock_irq(rq);
- resched_curr(rq);
- raw_spin_rq_unlock_irq(rq);
- }
+ for_each_cpu(cpu, resched_mask)
+ resched_cpu(cpu);
for_each_cpu_and(cpu, cpu_online_mask, node_mask) {
u32 nr = READ_ONCE(cpu_rq(cpu)->scx.bypass_dsq.nr);
--
2.17.1