linux-kernel - [PATCH RT 2/4] sched: migrate_enable: Use sleeping

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Date:   Tue, 18 Jun 2019 20:19:06 -0500
From:   Scott Wood <swood@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Scott Wood <swood@...hat.com>
Subject: [PATCH RT 2/4] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep

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@...hat.com>
---
 include/linux/sched.h    | 4 ++--
 kernel/rcu/tree_plugin.h | 2 +-
 kernel/sched/core.c      | 2 ++
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e1ea2ea52feb..9b8334c24dad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -681,7 +681,7 @@ struct task_struct {
 	int				migrate_disable_atomic;
 # endif
 #endif
-#ifdef CONFIG_PREEMPT_RT_FULL
+#ifdef CONFIG_PREEMPT_RT_BASE
 	int				sleeping_lock;
 #endif
 
@@ -1870,7 +1870,7 @@ 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 4bac3e5ee1ab..5d63914b3687 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -311,7 +311,7 @@ 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 a8493ff60b67..fce7d574ab5b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7351,7 +7351,9 @@ void migrate_enable(void)
 			unpin_current_cpu();
 			preempt_lazy_enable();
 			preempt_enable();
+			sleeping_lock_inc();
 			stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
+			sleeping_lock_dec();
 			tlb_migrate_finish(p->mm);
 
 			return;
-- 
1.8.3.1