tracing: Fix potential deadlock in cpu hotplug with osnoise

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>

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index dee610e465b981c1a4dbfb525b9e738818eedcac..be6cf0bb3c030e9204300389782c96863606a9d1 100644 (file)
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2073,8 +2073,8 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy)
        if (!osnoise_has_registered_instances())
                return;
 
-       guard(mutex)(&interface_lock);
        guard(cpus_read_lock)();
+       guard(mutex)(&interface_lock);
 
        if (!cpu_online(cpu))
                return;
@@ -2237,11 +2237,11 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf,
        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;
 
@@ -2257,8 +2257,8 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf,
                        clear_bit(option, &osnoise_options);
        }
 
-       cpus_read_unlock();
        mutex_unlock(&interface_lock);
+       cpus_read_unlock();
 
        if (running)
                start_per_cpu_kthreads();
@@ -2345,16 +2345,16 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
        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();