linux-kernel - [PATCH RT 1/8] sched: migrate_enable: Use sleeping

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Message-Id: <20190727055638.20443-2-swood@redhat.com>
Date:   Sat, 27 Jul 2019 00:56:31 -0500
From:   Scott Wood <swood@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Scott Wood <swood@...hat.com>
Subject: [PATCH RT 1/8] 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 4e218f8d8048..ad23ab939b35 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
 
@@ -1873,7 +1873,7 @@ 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 d3c6542b306f..c3407707e367 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7405,7 +7405,9 @@ 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();
 			return;
 		}
 	}
-- 
1.8.3.1