On Fri, Nov 06, 2015 at 06:41:43PM -0800, Joonwoo Park wrote:
> On Fri, Nov 06, 2015 at 02:57:49PM +0100, Peter Zijlstra wrote:
> > On Tue, Oct 27, 2015 at 09:46:53PM -0700, Joonwoo Park wrote:
> > > @@ -1272,6 +1272,15 @@ void set_task_cpu(struct task_struct *p, unsigned 
> > > int new_cpu)
> > >   WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
> > >                   !p->on_rq);
> > >  
> > > + /*
> > > +  * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
> > > +  * because schedstat_wait_{start,end} rebase migrating task's wait_start
> > > +  * time relying on p->on_rq.
> > > +  */
> > > + WARN_ON_ONCE(p->state == TASK_RUNNING &&
> > > +              p->sched_class == &fair_sched_class &&
> > > +              (p->on_rq && !task_on_rq_migrating(p)));
> > > +
> > 
> > Why do we have to test p->on_rq? Would not ->state == RUNNING imply
> > that?
> > 
> 
> sched_fork() sets p->state = RUNNING before changing task cpu.
> Please let me know if you got better idea.

Ah, indeed. OK.
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