On 6/21/21 5:25 PM, Steven Rostedt wrote: > On Mon, 21 Jun 2021 13:34:44 +0200 > Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote: > >>> And of course, because get_online_cpus() is called within >>> trace_types_lock, doing this check is going to cause a lock inversion. >>> >> Yep! I tried to take the trace_type_lock here, and got the lockdep info about >> this problem. >> >>> The only thing I could think of is to wake up a worker thread to do the >>> work. That is, this just wakes the worker thread, then the worker grabs >>> the trace_types_lock, iterates through the cpu mask of expect running >>> threads, and then starts or kills them depending on the hwlat_busy >>> value. >> So, it will not wait for the kworker to run? > What wont wait? For example, at the shutdown, should the hotplug callback wait for the workqueue to run & kill the thread, or not? -- Daniel > -- Steve >
