Re: [PATCH] net: sched: dev_deactivate_many(): use msleep(1) instead of yield() to wait for outstanding qdisc_run calls

[Mike Galbraith]

On Thu, 2014-03-06 at 16:06 -0500, David Miller wrote: 
> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> Date: Wed,  5 Mar 2014 00:49:47 +0100
> 
> > @@ -839,7 +839,7 @@ void dev_deactivate_many(struct list_head *head)
> >  	/* Wait for outstanding qdisc_run calls. */
> >  	list_for_each_entry(dev, head, unreg_list)
> >  		while (some_qdisc_is_busy(dev))
> > -			yield();
> > +			msleep(1)
> >  }
> 
> I don't understand this.
> 
> yield() should really _mean_ yield.

It does, but yield() semantics make it useless for what you want to do..
and pretty much undefined for anything other than SCHED_FIFO.  If you
really want to give up the CPU to any old body, you have to sleep.

-Mike




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