From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Joel Fernandes <joel@joelfernandes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep
Date: Tue, 24 Sep 2019 11:35:16 -0500 [thread overview]
Message-ID: <b05494c96c039c348c0d3cb93d92fc1b77fe1dab.camel@redhat.com> (raw)
In-Reply-To: <20190924160554.5esplbmnzm4q4tew@linutronix.de>
On Tue, 2019-09-24 at 18:05 +0200, Sebastian Andrzej Siewior wrote:
> On 2019-09-24 10:47:36 [-0500], Scott Wood wrote:
> > When the stop machine finishes it will do a wake_up_process() via
> > complete(). Since this does not pass WF_LOCK_SLEEPER, saved_state will
> > be
> > cleared, and you'll have TASK_RUNNING when you get to other_func() and
> > schedule(), regardless of whether CPU1 sends wake_up() -- so this change
> > doesn't actually accomplish anything.
>
> True, I completely missed that part.
>
> > While as noted in the other thread I don't think these spurious wakeups
> > are
> > a huge problem, we could avoid them by doing stop_one_cpu_nowait() and
> > then
> > schedule() without messing with task state. Since we're stopping our
> > own
> > cpu, it should be guaranteed that the stopper has finished by the time
> > we
> > exit schedule().
>
> I remember loosing a state can be a problem. Lets say it is not "just"
> TASK_UNINTERRUPTIBLE -> TASK_RUNNING which sounds harmless but it is
> __TASK_TRACED and you lose it as part of unlocking siglock.
OK, sounds like stop_one_cpu_nowait() is the way to go then.
-Scott
next prev parent reply other threads:[~2019-09-24 16:35 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 16:57 [PATCH RT v3 0/5] RCU fixes Scott Wood
2019-09-11 16:57 ` [PATCH RT v3 1/5] rcu: Acquire RCU lock when disabling BHs Scott Wood
2019-09-12 22:09 ` Joel Fernandes
2019-09-17 7:44 ` Sebastian Andrzej Siewior
2019-09-17 14:06 ` Scott Wood
2019-09-17 14:42 ` Sebastian Andrzej Siewior
2019-09-17 16:12 ` Scott Wood
2019-09-23 16:41 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 2/5] sched: Rename sleeping_lock to rt_invol_sleep Scott Wood
2019-09-17 7:52 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep Scott Wood
2019-09-17 7:59 ` Sebastian Andrzej Siewior
2019-09-17 14:06 ` Scott Wood
2019-09-23 16:59 ` Scott Wood
2019-09-23 17:52 ` Sebastian Andrzej Siewior
2019-09-24 11:21 ` Sebastian Andrzej Siewior
2019-09-24 13:53 ` Scott Wood
2019-09-24 15:25 ` Sebastian Andrzej Siewior
2019-09-24 15:47 ` Scott Wood
2019-09-24 16:05 ` Sebastian Andrzej Siewior
2019-09-24 16:35 ` Scott Wood [this message]
2019-10-04 16:45 ` Sebastian Andrzej Siewior
2019-09-11 16:57 ` [PATCH RT v3 4/5] rcu: Disable use_softirq on PREEMPT_RT Scott Wood
2019-09-12 21:38 ` Joel Fernandes
2019-09-12 22:19 ` Joel Fernandes
2019-09-17 9:31 ` Sebastian Andrzej Siewior
2019-09-17 14:08 ` Scott Wood
2019-09-11 16:57 ` [PATCH RT v3 5/5] rcutorture: Avoid problematic critical section nesting on RT Scott Wood
2019-09-12 22:17 ` Joel Fernandes
2019-09-16 16:55 ` Scott Wood
2019-09-17 10:07 ` Sebastian Andrzej Siewior
2019-09-17 14:36 ` Scott Wood
2019-09-17 14:50 ` Sebastian Andrzej Siewior
2019-09-17 16:32 ` Scott Wood
2019-09-23 16:25 ` Sebastian Andrzej Siewior
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