Re: [PATCH V4 05/12] trace/hwlat: Support hotplug operations

[Steven Rostedt]

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?

-- Steve