[PATCH 6.12 202/244] tracing: Fix potential deadlock in cpu hotplug with osnoise

Greg Kroah-Hartman
2026-03-31T16:54:48Z

From: Luo Haiyang <luo.haiyang@zte.com.cn>

[ Upstream commit 1f9885732248d22f788e4992c739a98c88ab8a55 ]

The following sequence may leads deadlock in cpu hotplug:

task1 task2 task3
----- ----- -----

mutex_lock(&interface_lock)

[CPU GOING OFFLINE]

cpus_write_lock();
osnoise_cpu_die();
kthread_stop(task3);
wait_for_completion();

osnoise_sleep();
mutex_lock(&interface_lock);

cpus_read_lock();

[DEAD LOCK]

Fix by swap the order of cpus_read_lock() and mutex_lock(&interface_lock).

Cc: stable@vger.kernel.org
Cc: <mathieu.desnoyers@efficios.com>
Cc: <zhang.run@zte.com.cn>
Cc: <yang.tao172@zte.com.cn>
Cc: <ran.xiaokai@zte.com.cn>
Fixes: bce29ac9ce0bb ("trace: Add osnoise tracer")
Link: https://patch.msgid.link/20260326141953414bVSj33dAYktqp9Oiyizq8@zte.com.cn
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Luo Haiyang <luo.haiyang@zte.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/trace_osnoise.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2104,8 +2104,8 @@ static void osnoise_hotplug_workfn(struc
if (!osnoise_has_registered_instances())
return;

- guard(mutex)(&interface_lock);
guard(cpus_read_lock)();
+ guard(mutex)(&interface_lock);

if (!cpu_online(cpu))
return;
@@ -2268,11 +2268,11 @@ static ssize_t osnoise_options_write(str
if (running)
stop_per_cpu_kthreads();

- mutex_lock(&interface_lock);
/*
* avoid CPU hotplug operations that might read options.
*/
cpus_read_lock();
+ mutex_lock(&interface_lock);

retval = cnt;

@@ -2288,8 +2288,8 @@ static ssize_t osnoise_options_write(str
clear_bit(option, &osnoise_options);
}

- cpus_read_unlock();
mutex_unlock(&interface_lock);
+ cpus_read_unlock();

if (running)
start_per_cpu_kthreads();
@@ -2375,16 +2375,16 @@ osnoise_cpus_write(struct file *filp, co
if (running)
stop_per_cpu_kthreads();

- mutex_lock(&interface_lock);
/*
* osnoise_cpumask is read by CPU hotplug operations.
*/
cpus_read_lock();
+ mutex_lock(&interface_lock);

cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);

- cpus_read_unlock();
mutex_unlock(&interface_lock);
+ cpus_read_unlock();

if (running)
start_per_cpu_kthreads();