Re: [patch 02/13] workqueue: Provide work_on_cpu_safe()

[Peter Zijlstra]

On Fri, Apr 14, 2017 at 11:51:07AM +0200, Thomas Gleixner wrote:
> On Fri, 14 Apr 2017, Peter Zijlstra wrote:
> 
> > On Wed, Apr 12, 2017 at 10:07:28PM +0200, Thomas Gleixner wrote:
> > > +long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
> > > +{
> > > +	long ret = -ENODEV;
> > > +
> > > +	get_online_cpus();
> > > +	if (cpu_online(cpu))
> > > +		ret = work_on_cpu(cpu, fn, arg);
> > > +	put_online_cpus();
> > > +	return ret;
> > > +}
> > 
> > But doesn't workqueue have this lovelt 'feature' where it will unbind
> > per-cpu work and run it on random CPUs when hotplug happens?
> > 
> > That is, I think you need a flush_work() before put_online_cpus() if you
> > want to guarantee anything.
> 
> work_on_cpu() is sychnronous, it flushes already.

So much for being awake ...