From: Wei Li liwei391@huawei.com

The cpuhp online/offline processing race also exists in percpu-mode hwlat tracer in theory, apply the fix too. That is:

T1 | T2 [CPUHP_ONLINE] | cpu_device_down() hwlat_hotplug_workfn() | | cpus_write_lock() | takedown_cpu(1) | cpus_write_unlock() [CPUHP_OFFLINE] | cpus_read_lock() | start_kthread(1) | cpus_read_unlock() |

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Link: https://lore.kernel.org/20240924094515.3561410-5-liwei391@huawei.com Fixes: ba998f7d9531 ("trace/hwlat: Support hotplug operations") Signed-off-by: Wei Li liwei391@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_hwlat.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index b791524a6536..3bd6071441ad 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -520,6 +520,8 @@ static void hwlat_hotplug_workfn(struct work_struct *dummy) if (!hwlat_busy || hwlat_data.thread_mode != MODE_PER_CPU) goto out_unlock;

+ if (!cpu_online(cpu)) + goto out_unlock; if (!cpumask_test_cpu(cpu, tr->tracing_cpumask)) goto out_unlock;