Re: [PATCH v2 7/7] sched/core: Add debug code to catch missing update_rq_clock()

[Thomas Gleixner]

On Wed, 21 Sep 2016, Matt Fleming wrote:

> On Wed, 21 Sep, at 05:58:27PM, Petr Mladek wrote:
> > 
> > I am not sure how the above call chain is realistic. But adding
> > WARN_ON() into the scheduler paths is risky in general.
> 
> It's not clear to me why this should be the case. WARN_ON() calls have
> existed in the scheduler paths since forever.

Everything which end up in printk within a rq->lock held section has been
have been prone to deadlocks for a very long time. Guess why
printk_deferred (the former printk_sched) exists.

Thanks,

	tglx