6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wei Li <liwei391@xxxxxxxxxx>
commit 2a13ca2e8abb12ee43ada8a107dadca83f140937 upstream.
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@xxxxxxxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Link: https://lore.kernel.org/20240924094515.3561410-5-liwei391@xxxxxxxxxx
Fixes: ba998f7d9531 ("trace/hwlat: Support hotplug operations")
Signed-off-by: Wei Li <liwei391@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_hwlat.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -520,6 +520,8 @@ static void hwlat_hotplug_workfn(struct
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;
