From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Scott Wood <swood@redhat.com>
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 17:25:14 +0200 [thread overview]
Message-ID: <20190924152514.enzeuoo5a6o3mgqu@linutronix.de> (raw)
In-Reply-To: <55dc19fcc44b2e658b71f68206306c8310335564.camel@redhat.com>
On 2019-09-24 08:53:43 [-0500], Scott Wood wrote:
> As I pointed out in the "[PATCH RT 6/8] sched: migrate_enable: Set state to
> TASK_RUNNING" discussion, we can get here inside the rtmutex code (e.g. from
> debug_rt_mutex_print_deadlock) where saved_state is already holding
> something -- plus, the waker won't have WF_LOCK_SLEEPER and therefore
> saved_state will get cleared anyway.
So let me drop the saved_state pieces and get back to it once I get to
the other thread (which you replied and I didn't realised until now).
Regarding the WF_LOCK_SLEEPER part. I think this works as expected.
Imagine:
CPU0 CPU1
spin_lock();
set_current_state(TASK_UNINTERRUPTIBLE);
…
spin_unlock()
-> migrate_enable();
-> stop_one_cpu(); <-- A)
other_func(); <-- B)
schedule();
So. With only CPU0 we enter schedule() with TASK_UNINTERRUPTIBLE because
the state gets preserved with the change I added (which is expected).
If CPU1 sends a wake_up() at A) then the saved_state gets overwritten
and we enter schedule() with TASK_RUNNING. Same happens if it is sent at
B) point which is outside of any migrate/spin lock related code.
Was this clear or did I miss the point?
> -Scott
Sebastian
next prev parent reply other threads:[~2019-09-24 15:25 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 [this message]
2019-09-24 15:47 ` Scott Wood
2019-09-24 16:05 ` Sebastian Andrzej Siewior
2019-09-24 16:35 ` Scott Wood
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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