On Thu 22-09-16 10:04:36, Peter Zijlstra wrote:
> On Wed, Sep 21, 2016 at 05:58:27PM +0200, Petr Mladek wrote:
> > > +static inline void assert_clock_updated(struct rq *rq)
> > > +{
> > > +#ifdef CONFIG_SCHED_DEBUG
> > > + /*
> > > + * The only reason for not seeing a clock update since the
> > > + * last rq_pin_lock() is if we're currently skipping updates.
> > > + */
> > > + WARN_ON_ONCE(rq->clock_update_flags < RQCF_ACT_SKIP);
> > > +#endif
> > > +}
> >
> > I am afraid that it might eventually create a deadlock.
> > For example, there is the following call chain:
> >
>
> Yeah, meh. There's already plenty WARNs in the sched code. The idea of
> course being that they should not trigger. If they do, something
> buggered already, so who bloody cares about a deadlock later ;-)
Yeah, the trouble is that you usually won't see the WARN message
before deadlocking. So WARN_ON in scheduler is usually equivalent to
if (condition)
while (1);
;) Not really helping debugging much...
Honza
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
