From: Thomas Gleixner <tglx@linutronix.de>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH RT 4/6] rt/locking: Reenable migration accross schedule
Date: Fri, 25 Mar 2016 09:52:49 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1603250951100.3978@nanos> (raw)
In-Reply-To: <1458884330.3836.21.camel@gmail.com>
On Fri, 25 Mar 2016, Mike Galbraith wrote:
> On Thu, 2016-03-24 at 12:06 +0100, Mike Galbraith wrote:
> > On Thu, 2016-03-24 at 11:44 +0100, Thomas Gleixner wrote:
> > >
> > > > On the bright side, with the busted migrate enable business reverted,
> > > > plus one dinky change from me [1], master-rt.today has completed 100
> > > > iterations of Steven's hotplug stress script along side endless
> > > > futexstress, and is happily doing another 900 as I write this, so the
> > > > next -rt should finally be hotplug deadlock free.
> > > >
> > > > Thomas's state machinery seems to work wonders. 'course this being
> > > > hotplug, the other shoe will likely apply itself to my backside soon.
> > >
> > > That's a given :)
> >
> > blk-mq applied it shortly after I was satisfied enough to poke xmit.
>
> The other shoe is that notifiers can depend upon RCU grace periods, so
> when pin_current_cpu() snags rcu_sched, the hotplug game is over.
>
> blk_mq_queue_reinit_notify:
> /*
> * We need to freeze and reinit all existing queues. Freezing
> * involves synchronous wait for an RCU grace period and doing it
> * one by one may take a long time. Start freezing all queues in
> * one swoop and then wait for the completions so that freezing can
> * take place in parallel.
> */
> list_for_each_entry(q, &all_q_list, all_q_node)
> blk_mq_freeze_queue_start(q);
> list_for_each_entry(q, &all_q_list, all_q_node) {
> blk_mq_freeze_queue_wait(q);
Yeah, I stumbled over that already when analysing all the hotplug notifier
sites. That's definitely a horrible one.
> Hohum (sharpens rock), next.
/me recommends frozen sharks
Thanks,
tglx
next prev parent reply other threads:[~2016-03-25 8:54 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-12 23:02 [PATCH RT 1/6] kernel: softirq: unlock with irqs on Sebastian Andrzej Siewior
2016-02-12 23:02 ` [PATCH RT 2/6] kernel: migrate_disable() do fastpath in atomic & irqs-off Sebastian Andrzej Siewior
2016-02-12 23:02 ` [PATCH RT 3/6] rtmutex: push down migrate_disable() into rt_spin_lock() Sebastian Andrzej Siewior
2016-02-12 23:02 ` [PATCH RT 4/6] rt/locking: Reenable migration accross schedule Sebastian Andrzej Siewior
2016-03-20 8:43 ` Mike Galbraith
2016-03-24 10:07 ` Mike Galbraith
2016-03-24 10:44 ` Thomas Gleixner
2016-03-24 11:06 ` Mike Galbraith
2016-03-25 5:38 ` Mike Galbraith
2016-03-25 8:52 ` Thomas Gleixner [this message]
2016-03-25 9:13 ` Mike Galbraith
2016-03-25 9:14 ` Mike Galbraith
2016-03-25 16:24 ` Mike Galbraith
2016-03-29 4:05 ` Mike Galbraith
2016-03-31 6:31 ` Mike Galbraith
2016-04-01 21:11 ` Sebastian Andrzej Siewior
2016-04-02 3:12 ` Mike Galbraith
2016-04-05 12:49 ` [rfc patch 0/2] Kill hotplug_lock()/hotplug_unlock() Mike Galbraith
[not found] ` <1459837988.26938.16.camel@gmail.com>
2016-04-05 12:49 ` [rfc patch 1/2] rt/locking/hotplug: " Mike Galbraith
2016-04-05 12:49 ` [rfc patch 2/2] rt/locking/hotplug: Fix rt_spin_lock_slowlock() migrate_disable() bug Mike Galbraith
2016-04-06 12:00 ` Mike Galbraith
2016-04-07 4:37 ` Mike Galbraith
2016-04-07 16:48 ` Sebastian Andrzej Siewior
2016-04-07 19:08 ` Mike Galbraith
2016-04-07 16:47 ` [PATCH RT 4/6] rt/locking: Reenable migration accross schedule Sebastian Andrzej Siewior
2016-04-07 19:04 ` Mike Galbraith
2016-04-08 10:30 ` Sebastian Andrzej Siewior
2016-04-08 12:10 ` Mike Galbraith
2016-04-08 6:35 ` Mike Galbraith
2016-04-08 13:44 ` Mike Galbraith
2016-04-08 13:58 ` Sebastian Andrzej Siewior
2016-04-08 14:16 ` Mike Galbraith
2016-04-08 14:51 ` Sebastian Andrzej Siewior
2016-04-08 16:49 ` Mike Galbraith
2016-04-18 17:15 ` Sebastian Andrzej Siewior
2016-04-18 17:55 ` Mike Galbraith
2016-04-19 7:07 ` Sebastian Andrzej Siewior
2016-04-19 8:55 ` Mike Galbraith
2016-04-19 9:02 ` Sebastian Andrzej Siewior
2016-02-12 23:02 ` [PATCH RT 5/6] kernel/stop_machine: partly revert "stop_machine: Use raw spinlocks" Sebastian Andrzej Siewior
2016-02-12 23:02 ` [PATCH RT 6/6] rcu: disable more spots of rcu_bh Sebastian Andrzej Siewior
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