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Method (two sessions per build): 5 runs per session, 5 offline/online pairs per run. Per pair: taskset 0x8 sh -c 'n=0; while [ $n -lt 100 ]; do sleep 0.01; n=$((n+1)); done' & sleep 0.5 echo 0 > /sys/devices/system/cpu/cpu3/online echo 1 > /sys/devices/system/cpu/cpu3/online wait # then the same sleep loop again Temporary debug dmesg counts per run: empty_bucket - collect_expired_timers() saw pending_map bit set with an empty hlist (next_expiry had been pulled to a stale empty bucket after re-online) stale_pending - timers_dead_cpu() saw non-empty pending_map after migrate (same probe on both builds; Build A then clears, Build B does not) Build A: clear pending_map after migrate Build B: do not clear Build A session 1 / 2 (empty_bucket, stale_pending): 0,6 0,6 0,6 0,6 0,5 0,7 0,5 0,5 0,5 0,5 Build B session 1 / 2: 33,10 18,10 10,10 12,10 6,10 32,10 14,10 17,10 13,10 10,10 stale_pending > 0 on both builds is expected: migrate leaves bits set while vectors are empty. Build A clears them; Build B leaves them. The discriminator is empty_bucket: without clearing it is > 0 every run; with clearing it stays 0. Thanks, Liang Hao