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From 3b5e53770c3aff121339c47e7fe3888ee6ffef7c Mon Sep 17 00:00:00 2001
Message-Id: <3b5e53770c3aff121339c47e7fe3888ee6ffef7c.1601675152.git.zanussi@kernel.org>
In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 21 Sep 2017 14:25:13 +0200
Subject: [PATCH 154/333] rtmutex: annotate sleeping lock context
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
The RCU code complains on schedule() within a rcu_readlock() section.
The valid scenario on -RT is if a sleeping is held. In order to suppress
the warning the mirgrate_disable counter was used to identify the
invocation of schedule() due to lock contention.
Grygorii Strashko report that during CPU hotplug we might see the
warning via
rt_spin_lock() -> migrate_disable() -> pin_current_cpu() -> __read_rt_lock()
because the counter is not yet set.
It is also possible to trigger the warning from cpu_chill()
(seen on a kblockd_mod_delayed_work_on() caller).
To address this RCU warning I annotate the sleeping lock context. The
counter is incremented before migrate_disable() so the warning Grygorii
should not trigger anymore. Additionally I use that counter in
cpu_chill() to avoid the RCU warning from there.
Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/preempt.h | 9 ++++++++
include/linux/sched.h | 26 ++++++++++++++++++++++
kernel/locking/rtmutex.c | 12 ++++++++--
kernel/locking/rwlock-rt.c | 18 +++++++++++----
kernel/rcu/tree_plugin.h | 6 ++++-
kernel/sched/core.c | 45 ++++++++++++++++++++++++++++++++++++++
6 files changed, 109 insertions(+), 7 deletions(-)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 27c3176d88d2..9eafc34898b4 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -211,6 +211,15 @@ extern void migrate_enable(void);
int __migrate_disabled(struct task_struct *p);
+#elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE)
+
+extern void migrate_disable(void);
+extern void migrate_enable(void);
+static inline int __migrate_disabled(struct task_struct *p)
+{
+ return 0;
+}
+
#else
#define migrate_disable() barrier()
#define migrate_enable() barrier()
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d207f79c2ecb..50197f5c4506 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -673,6 +673,15 @@ struct task_struct {
# ifdef CONFIG_SCHED_DEBUG
int migrate_disable_atomic;
# endif
+
+#elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE)
+ int migrate_disable;
+# ifdef CONFIG_SCHED_DEBUG
+ int migrate_disable_atomic;
+# endif
+#endif
+#ifdef CONFIG_PREEMPT_RT_FULL
+ int sleeping_lock;
#endif
#ifdef CONFIG_PREEMPT_RCU
@@ -1810,6 +1819,23 @@ static __always_inline bool need_resched(void)
return unlikely(tif_need_resched());
}
+#ifdef CONFIG_PREEMPT_RT_FULL
+static inline void sleeping_lock_inc(void)
+{
+ current->sleeping_lock++;
+}
+
+static inline void sleeping_lock_dec(void)
+{
+ current->sleeping_lock--;
+}
+
+#else
+
+static inline void sleeping_lock_inc(void) { }
+static inline void sleeping_lock_dec(void) { }
+#endif
+
/*
* Wrappers for p->thread_info->cpu access. No-op on UP.
*/
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 94788662b2f2..2a9bf2443acc 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1141,6 +1141,7 @@ void __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
void __lockfunc rt_spin_lock(spinlock_t *lock)
{
+ sleeping_lock_inc();
migrate_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
@@ -1155,6 +1156,7 @@ void __lockfunc __rt_spin_lock(struct rt_mutex *lock)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass)
{
+ sleeping_lock_inc();
migrate_disable();
spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
@@ -1168,6 +1170,7 @@ void __lockfunc rt_spin_unlock(spinlock_t *lock)
spin_release(&lock->dep_map, 1, _RET_IP_);
rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock);
migrate_enable();
+ sleeping_lock_dec();
}
EXPORT_SYMBOL(rt_spin_unlock);
@@ -1193,12 +1196,15 @@ int __lockfunc rt_spin_trylock(spinlock_t *lock)
{
int ret;
+ sleeping_lock_inc();
migrate_disable();
ret = __rt_mutex_trylock(&lock->lock);
- if (ret)
+ if (ret) {
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
- else
+ } else {
migrate_enable();
+ sleeping_lock_dec();
+ }
return ret;
}
EXPORT_SYMBOL(rt_spin_trylock);
@@ -1210,6 +1216,7 @@ int __lockfunc rt_spin_trylock_bh(spinlock_t *lock)
local_bh_disable();
ret = __rt_mutex_trylock(&lock->lock);
if (ret) {
+ sleeping_lock_inc();
migrate_disable();
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
} else
@@ -1225,6 +1232,7 @@ int __lockfunc rt_spin_trylock_irqsave(spinlock_t *lock, unsigned long *flags)
*flags = 0;
ret = __rt_mutex_trylock(&lock->lock);
if (ret) {
+ sleeping_lock_inc();
migrate_disable();
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
}
diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c
index 8f90afe111ce..c3b91205161c 100644
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -305,12 +305,15 @@ int __lockfunc rt_read_trylock(rwlock_t *rwlock)
{
int ret;
+ sleeping_lock_inc();
migrate_disable();
ret = do_read_rt_trylock(rwlock);
- if (ret)
+ if (ret) {
rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
- else
+ } else {
migrate_enable();
+ sleeping_lock_dec();
+ }
return ret;
}
EXPORT_SYMBOL(rt_read_trylock);
@@ -319,18 +322,22 @@ int __lockfunc rt_write_trylock(rwlock_t *rwlock)
{
int ret;
+ sleeping_lock_inc();
migrate_disable();
ret = do_write_rt_trylock(rwlock);
- if (ret)
+ if (ret) {
rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
- else
+ } else {
migrate_enable();
+ sleeping_lock_dec();
+ }
return ret;
}
EXPORT_SYMBOL(rt_write_trylock);
void __lockfunc rt_read_lock(rwlock_t *rwlock)
{
+ sleeping_lock_inc();
migrate_disable();
rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
do_read_rt_lock(rwlock);
@@ -339,6 +346,7 @@ EXPORT_SYMBOL(rt_read_lock);
void __lockfunc rt_write_lock(rwlock_t *rwlock)
{
+ sleeping_lock_inc();
migrate_disable();
rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
do_write_rt_lock(rwlock);
@@ -350,6 +358,7 @@ void __lockfunc rt_read_unlock(rwlock_t *rwlock)
rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
do_read_rt_unlock(rwlock);
migrate_enable();
+ sleeping_lock_dec();
}
EXPORT_SYMBOL(rt_read_unlock);
@@ -358,6 +367,7 @@ void __lockfunc rt_write_unlock(rwlock_t *rwlock)
rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
do_write_rt_unlock(rwlock);
migrate_enable();
+ sleeping_lock_dec();
}
EXPORT_SYMBOL(rt_write_unlock);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 5f6de49dc78e..35f3552b7463 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -337,9 +337,13 @@ static void rcu_preempt_note_context_switch(bool preempt)
struct task_struct *t = current;
struct rcu_data *rdp;
struct rcu_node *rnp;
+ int sleeping_l = 0;
lockdep_assert_irqs_disabled();
- WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0);
+#if defined(CONFIG_PREEMPT_RT_FULL)
+ sleeping_l = t->sleeping_lock;
+#endif
+ WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0 && !sleeping_l);
if (t->rcu_read_lock_nesting > 0 &&
!t->rcu_read_unlock_special.b.blocked) {
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3128a5b95fd7..d10698fa8cad 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7349,4 +7349,49 @@ void migrate_enable(void)
preempt_enable();
}
EXPORT_SYMBOL(migrate_enable);
+
+#elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE)
+void migrate_disable(void)
+{
+ struct task_struct *p = current;
+
+ if (in_atomic() || irqs_disabled()) {
+#ifdef CONFIG_SCHED_DEBUG
+ p->migrate_disable_atomic++;
+#endif
+ return;
+ }
+#ifdef CONFIG_SCHED_DEBUG
+ if (unlikely(p->migrate_disable_atomic)) {
+ tracing_off();
+ WARN_ON_ONCE(1);
+ }
+#endif
+
+ p->migrate_disable++;
+}
+EXPORT_SYMBOL(migrate_disable);
+
+void migrate_enable(void)
+{
+ struct task_struct *p = current;
+
+ if (in_atomic() || irqs_disabled()) {
+#ifdef CONFIG_SCHED_DEBUG
+ p->migrate_disable_atomic--;
+#endif
+ return;
+ }
+
+#ifdef CONFIG_SCHED_DEBUG
+ if (unlikely(p->migrate_disable_atomic)) {
+ tracing_off();
+ WARN_ON_ONCE(1);
+ }
+#endif
+
+ WARN_ON_ONCE(p->migrate_disable <= 0);
+ p->migrate_disable--;
+}
+EXPORT_SYMBOL(migrate_enable);
#endif
--
2.17.1
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