If the task happens to run after cpu hot-plug offline, then it would not
be running in a percpu_thread. Instead, it would be re-queued into a
UNBOUND workqueue. This would trigger a warning if we enable kernel
preemption.
Signed-off-by: Andy Chiu <andy.c...@sifive.com>
---
kernel/trace/trace_hwlat.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index b791524a6536..87258ddc2141 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -511,7 +511,16 @@ static int start_cpu_kthread(unsigned int cpu)
static void hwlat_hotplug_workfn(struct work_struct *dummy)
{
struct trace_array *tr = hwlat_trace;
- unsigned int cpu = smp_processor_id();
+ unsigned int cpu;
+
+ /*
+ * If the work is scheduled after CPU hotplug offline being invoked,
+ * then it would be queued into UNBOUNDED workqueue
+ */
+ if (!is_percpu_thread())
+ return;
+
+ cpu = smp_processor_id();
mutex_lock(&trace_types_lock);
mutex_lock(&hwlat_data.lock);
--
2.43.0
