From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Scott Wood <swood@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Joel Fernandes <joel@joelfernandes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH RT v2 2/3] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep
Date: Wed, 21 Aug 2019 16:35:55 -0700 [thread overview]
Message-ID: <20190821233555.GV28441@linux.ibm.com> (raw)
In-Reply-To: <20190821231906.4224-3-swood@redhat.com>
On Wed, Aug 21, 2019 at 06:19:05PM -0500, Scott Wood wrote:
> Without this, rcu_note_context_switch() will complain if an RCU read
> lock is held when migrate_enable() calls stop_one_cpu().
>
> Signed-off-by: Scott Wood <swood@redhat.com>
I have to ask... Both sleeping_lock_inc() and sleeping_lock_dec() are
no-ops if not CONFIG_PREEMPT_RT_BASE?
Thanx, Paul
> ---
> v2: Added comment.
>
> If my migrate disable changes aren't taken, then pin_current_cpu()
> will also need to use sleeping_lock_inc() because calling
> __read_rt_lock() bypasses the usual place it's done.
>
> include/linux/sched.h | 4 ++--
> kernel/rcu/tree_plugin.h | 2 +-
> kernel/sched/core.c | 8 ++++++++
> 3 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 7e892e727f12..1ebc97f28009 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -673,7 +673,7 @@ struct task_struct {
> int migrate_disable_atomic;
> # endif
> #endif
> -#ifdef CONFIG_PREEMPT_RT_FULL
> +#ifdef CONFIG_PREEMPT_RT_BASE
> int sleeping_lock;
> #endif
>
> @@ -1881,7 +1881,7 @@ static __always_inline bool need_resched(void)
> return unlikely(tif_need_resched());
> }
>
> -#ifdef CONFIG_PREEMPT_RT_FULL
> +#ifdef CONFIG_PREEMPT_RT_BASE
> static inline void sleeping_lock_inc(void)
> {
> current->sleeping_lock++;
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 23a54e4b649c..7a3aa085ce2c 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -292,7 +292,7 @@ void rcu_note_context_switch(bool preempt)
> barrier(); /* Avoid RCU read-side critical sections leaking down. */
> trace_rcu_utilization(TPS("Start context switch"));
> lockdep_assert_irqs_disabled();
> -#if defined(CONFIG_PREEMPT_RT_FULL)
> +#if defined(CONFIG_PREEMPT_RT_BASE)
> sleeping_l = t->sleeping_lock;
> #endif
> WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0 && !sleeping_l);
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index e1bdd7f9be05..0758ee85634e 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7405,7 +7405,15 @@ void migrate_enable(void)
> unpin_current_cpu();
> preempt_lazy_enable();
> preempt_enable();
> +
> + /*
> + * sleeping_lock_inc suppresses a debug check for
> + * sleeping inside an RCU read side critical section
> + */
> + sleeping_lock_inc();
> stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
> + sleeping_lock_dec();
> +
> return;
> }
> }
> --
> 1.8.3.1
>
next prev parent reply other threads:[~2019-08-21 23:36 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 23:19 [PATCH RT v2 0/3] RCU fixes Scott Wood
2019-08-21 23:19 ` [PATCH RT v2 1/3] rcu: Acquire RCU lock when disabling BHs Scott Wood
2019-08-21 23:33 ` Paul E. McKenney
2019-08-22 13:39 ` Joel Fernandes
2019-08-22 15:27 ` Paul E. McKenney
2019-08-23 1:50 ` Joel Fernandes
2019-08-23 2:11 ` Paul E. McKenney
2019-08-23 3:23 ` Scott Wood
2019-08-23 12:30 ` Paul E. McKenney
2019-08-23 16:17 ` Sebastian Andrzej Siewior
2019-08-23 19:46 ` Scott Wood
2019-08-26 15:59 ` Sebastian Andrzej Siewior
2019-08-26 23:21 ` Scott Wood
2019-08-23 2:36 ` Scott Wood
2019-08-23 2:54 ` Paul E. McKenney
2019-08-21 23:19 ` [PATCH RT v2 2/3] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Scott Wood
2019-08-21 23:35 ` Paul E. McKenney [this message]
2019-08-23 1:21 ` Scott Wood
2019-08-23 16:20 ` Sebastian Andrzej Siewior
2019-08-23 19:28 ` Scott Wood
2019-08-24 3:10 ` Joel Fernandes
2019-08-26 15:25 ` Sebastian Andrzej Siewior
2019-08-26 16:29 ` Paul E. McKenney
2019-08-26 17:49 ` Scott Wood
2019-08-26 18:12 ` Paul E. McKenney
2019-08-27 9:23 ` Sebastian Andrzej Siewior
2019-08-27 13:08 ` Joel Fernandes
2019-08-27 15:58 ` Paul E. McKenney
2019-08-27 16:06 ` Joel Fernandes
2019-08-27 15:53 ` Paul E. McKenney
2019-08-28 9:27 ` Sebastian Andrzej Siewior
2019-08-28 12:54 ` Paul E. McKenney
2019-08-28 13:14 ` Sebastian Andrzej Siewior
2019-08-28 13:59 ` Joel Fernandes
2019-08-28 15:51 ` Paul E. McKenney
2019-08-28 15:50 ` Paul E. McKenney
2019-08-21 23:19 ` [PATCH RT v2 3/3] rcu: Disable use_softirq on PREEMPT_RT Scott Wood
2019-08-21 23:40 ` Paul E. McKenney
2019-08-23 16:32 ` Sebastian Andrzej Siewior
2019-08-22 13:59 ` Joel Fernandes
2019-08-22 15:29 ` Paul E. McKenney
2019-08-22 19:31 ` Scott Wood
2019-08-23 0:52 ` Joel Fernandes
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