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sched_ext: Fix timer pinning and return value in scx_central

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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: 22a920209a ("sched_ext: Implement tickless support")
Signed-off-by: Wanwu Li <liwanwu@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Wanwu Li 2026-08-27 16:07:36 +08:00 committed by Tejun Heo
parent 6586705bc2
commit 2376135986
1 changed files with 5 additions and 1 deletions
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6
tools/sched_ext/scx_central.bpf.c
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@ -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;
}