From 23761359861ca4bb087540937dfea8b0716914c2 Mon Sep 17 00:00:00 2001 From: Wanwu Li Date: Thu, 27 Aug 2026 16:07:36 +0800 Subject: [PATCH] sched_ext: Fix timer pinning and return value in scx_central central_timerfn() re-arms the timer with a hardcoded BPF_F_TIMER_CPU_PIN flag and ignores the return value, defeating start_central_timer()'s -EINVAL fallback for kernels without the flag (<6.7): on such kernels the first tick kills the timer permanently with no diagnostic. Honor timer_pinned and check the return like the initial arm does. Fixes: 22a920209ab6 ("sched_ext: Implement tickless support") Signed-off-by: Wanwu Li Signed-off-by: Tejun Heo --- tools/sched_ext/scx_central.bpf.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/tools/sched_ext/scx_central.bpf.c b/tools/sched_ext/scx_central.bpf.c index 64dd60b3e922..65dae9e45400 100644 --- a/tools/sched_ext/scx_central.bpf.c +++ b/tools/sched_ext/scx_central.bpf.c @@ -299,6 +299,7 @@ static int central_timerfn(void *map, int *key, struct bpf_timer *timer) u64 now = scx_bpf_now(); u64 nr_to_kick = nr_queued; s32 i, curr_cpu; + int ret; curr_cpu = bpf_get_smp_processor_id(); if (timer_pinned && (curr_cpu != central_cpu)) { @@ -332,7 +333,10 @@ static int central_timerfn(void *map, int *key, struct bpf_timer *timer) scx_bpf_kick_cpu(cpu, SCX_KICK_PREEMPT); } - bpf_timer_start(timer, TIMER_INTERVAL_NS, BPF_F_TIMER_CPU_PIN); + ret = bpf_timer_start(timer, TIMER_INTERVAL_NS, + timer_pinned ? BPF_F_TIMER_CPU_PIN : 0); + if (ret) + scx_bpf_error("bpf_timer_start failed (%d)", ret); __sync_fetch_and_add(&nr_timers, 1); return 0; }