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Message-ID: <20160922080436.GX5008@twins.programming.kicks-ass.net>
Date: Thu, 22 Sep 2016 10:04:36 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Petr Mladek <pmladek@...e.com>
Cc: Matt Fleming <matt@...eblueprint.co.uk>,
Ingo Molnar <mingo@...nel.org>,
Byungchul Park <byungchul.park@....com>,
Frederic Weisbecker <fweisbec@...il.com>,
Luca Abeni <luca.abeni@...tn.it>,
Rik van Riel <riel@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Wanpeng Li <wanpeng.li@...mail.com>,
Yuyang Du <yuyang.du@...el.com>, Jan Kara <jack@...e.cz>,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
linux-kernel@...r.kernel.org,
Mel Gorman <mgorman@...hsingularity.net>,
Mike Galbraith <umgwanakikbuti@...il.com>
Subject: Re: [PATCH v2 7/7] sched/core: Add debug code to catch missing
update_rq_clock()
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 ;-)
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