1 files changed, 117 insertions, 0 deletions
diff --git a/debian/patches-rt/locking-Make-spinlock_t-and-rwlock_t-a-RCU-section-o.patch b/debian/patches-rt/locking-Make-spinlock_t-and-rwlock_t-a-RCU-section-o.patch
new file mode 100644
index 000000000..6590fba76
--- /dev/null
+++ b/debian/patches-rt/locking-Make-spinlock_t-and-rwlock_t-a-RCU-section-o.patch
@@ -0,0 +1,117 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Tue, 19 Nov 2019 09:25:04 +0100
+Subject: [PATCH] locking: Make spinlock_t and rwlock_t a RCU section on RT
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz
+
+On !RT a locked spinlock_t and rwlock_t disables preemption which
+implies a RCU read section. There is code that relies on that behaviour.
+
+Add an explicit RCU read section on RT while a sleeping lock (a lock
+which would disables preemption on !RT) acquired.
+
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/locking/rtmutex.c   |    6 ++++++
+ kernel/locking/rwlock-rt.c |    6 ++++++
+ 2 files changed, 12 insertions(+)
+
+--- a/kernel/locking/rtmutex.c
++++ b/kernel/locking/rtmutex.c
+@@ -1141,6 +1141,7 @@ void __sched rt_spin_lock_slowunlock(str
+ void __lockfunc rt_spin_lock(spinlock_t *lock)
+ {
+ 	sleeping_lock_inc();
++	rcu_read_lock();
+ 	migrate_disable();
+ 	spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+ 	rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
+@@ -1156,6 +1157,7 @@ void __lockfunc __rt_spin_lock(struct rt
+ void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass)
+ {
+ 	sleeping_lock_inc();
++	rcu_read_lock();
+ 	migrate_disable();
+ 	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
+ 	rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
+@@ -1169,6 +1171,7 @@ void __lockfunc rt_spin_unlock(spinlock_
+ 	spin_release(&lock->dep_map, 1, _RET_IP_);
+ 	rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock);
+ 	migrate_enable();
++	rcu_read_unlock();
+ 	sleeping_lock_dec();
+ }
+ EXPORT_SYMBOL(rt_spin_unlock);
+@@ -1200,6 +1203,7 @@ int __lockfunc rt_spin_trylock(spinlock_
+ 	ret = __rt_mutex_trylock(&lock->lock);
+ 	if (ret) {
+ 		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
++		rcu_read_lock();
+ 	} else {
+ 		migrate_enable();
+ 		sleeping_lock_dec();
+@@ -1216,6 +1220,7 @@ int __lockfunc rt_spin_trylock_bh(spinlo
+ 	ret = __rt_mutex_trylock(&lock->lock);
+ 	if (ret) {
+ 		sleeping_lock_inc();
++		rcu_read_lock();
+ 		migrate_disable();
+ 		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+ 	} else
+@@ -1232,6 +1237,7 @@ int __lockfunc rt_spin_trylock_irqsave(s
+ 	ret = __rt_mutex_trylock(&lock->lock);
+ 	if (ret) {
+ 		sleeping_lock_inc();
++		rcu_read_lock();
+ 		migrate_disable();
+ 		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+ 	}
+--- a/kernel/locking/rwlock-rt.c
++++ b/kernel/locking/rwlock-rt.c
+@@ -310,6 +310,7 @@ int __lockfunc rt_read_trylock(rwlock_t
+ 	ret = do_read_rt_trylock(rwlock);
+ 	if (ret) {
+ 		rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
++		rcu_read_lock();
+ 	} else {
+ 		migrate_enable();
+ 		sleeping_lock_dec();
+@@ -327,6 +328,7 @@ int __lockfunc rt_write_trylock(rwlock_t
+ 	ret = do_write_rt_trylock(rwlock);
+ 	if (ret) {
+ 		rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
++		rcu_read_lock();
+ 	} else {
+ 		migrate_enable();
+ 		sleeping_lock_dec();
+@@ -338,6 +340,7 @@ EXPORT_SYMBOL(rt_write_trylock);
+ void __lockfunc rt_read_lock(rwlock_t *rwlock)
+ {
+ 	sleeping_lock_inc();
++	rcu_read_lock();
+ 	migrate_disable();
+ 	rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
+ 	do_read_rt_lock(rwlock);
+@@ -347,6 +350,7 @@ EXPORT_SYMBOL(rt_read_lock);
+ void __lockfunc rt_write_lock(rwlock_t *rwlock)
+ {
+ 	sleeping_lock_inc();
++	rcu_read_lock();
+ 	migrate_disable();
+ 	rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
+ 	do_write_rt_lock(rwlock);
+@@ -358,6 +362,7 @@ void __lockfunc rt_read_unlock(rwlock_t
+ 	rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
+ 	do_read_rt_unlock(rwlock);
+ 	migrate_enable();
++	rcu_read_unlock();
+ 	sleeping_lock_dec();
+ }
+ EXPORT_SYMBOL(rt_read_unlock);
+@@ -367,6 +372,7 @@ void __lockfunc rt_write_unlock(rwlock_t
+ 	rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
+ 	do_write_rt_unlock(rwlock);
+ 	migrate_enable();
++	rcu_read_unlock();
+ 	sleeping_lock_dec();
+ }
+ EXPORT_SYMBOL(rt_write_unlock);