Commit 1f988573 authored by Luo Haiyang's avatar Luo Haiyang Committed by Steven Rostedt (Google)
Browse files

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: bce29ac9 ("trace: Add osnoise tracer")
Link: https://patch.msgid.link/20260326141953414bVSj33dAYktqp9Oiyizq8@zte.com.cn


Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarLuo Haiyang <luo.haiyang@zte.com.cn>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 50b35c9e

kernel/trace/trace_osnoise.c

+5 −5
Original line number Diff line number Diff line
@@ -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();