Messages in this thread | | | Date | Thu, 22 Sep 2016 10:36:37 +0200 | From | Jan Kara <> | Subject | Re: [PATCH v2 7/7] sched/core: Add debug code to catch missing update_rq_clock() |
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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 <jack@suse.com> SUSE Labs, CR
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