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

[Thomas Gleixner]

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.

Thanks,

	tglx