linux-kernel - Re: Boot failure on emev2/kzm9d (was: Re: [PATCH v2 11/11] mm/slab: lockless decision to grow cache)

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Date:	Thu, 30 Jun 2016 19:54:56 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...nel.org>,
	Linux MM <linux-mm@...ck.org>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Boot failure on emev2/kzm9d (was: Re: [PATCH v2 11/11] mm/slab:
 lockless decision to grow cache)

Hi Paul,

On Thu, Jun 30, 2016 at 6:52 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Thu, Jun 30, 2016 at 05:53:42PM +0200, Geert Uytterhoeven wrote:
>> +void rcu_dump_rcu_sched_tree(void)
>> +{
>> +     struct rcu_head rh;
>> +     unsigned long flags;
>> +
>> +     rcu_dump_rcu_node_tree(&rcu_sched_state);  /* Initial state. */
>> +     local_irq_save(flags);
>> +     // call_rcu(&rh, do_nothing_cb);
>> +     local_irq_restore(flags);
>> +     // schedule_timeout_uninterruptible(5 * HZ);  /* Or whatever delay. */
>> +     rcu_dump_rcu_node_tree(&rcu_sched_state); /* GP state. */
>> +     //synchronize_sched();  /* Probably hangs. */
>> +     //rcu_barrier();  /* Drop RCU's references to rh before return. */
>> +}

>>
>> When enabling any of the 4 commented-out lines in rcu_dump_rcu_sched_tree(),
>> it will lock up.
>
> OK, but that includes schedule_timeout_uninterruptible(5 * HZ), right?

Yes it does.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds