[PATCH 4/5] tracing/hwlat: Fix a race during cpuhp processing

[Wei Li]

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

Fixes: ba998f7d9531 ("trace/hwlat: Support hotplug operations")
Signed-off-by: Wei Li <liwei...@huawei.com>
---
 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;
 
-- 
2.25.1