From ee016d63cce75a97334f9867416f4e888e673d36 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 19 Nov 2019 09:25:04 +0100
Subject: [PATCH 228/327] locking: Make spinlock_t and rwlock_t a RCU section
 on RT

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(+)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 0893512f8769..bec7e07a80dc 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1136,6 +1136,7 @@ void __lockfunc rt_spin_lock(spinlock_t *lock)
 {
 	spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
 	rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
+	rcu_read_lock();
 	migrate_disable();
 }
 EXPORT_SYMBOL(rt_spin_lock);
@@ -1150,6 +1151,7 @@ void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass)
 {
 	spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
 	rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
+	rcu_read_lock();
 	migrate_disable();
 }
 EXPORT_SYMBOL(rt_spin_lock_nested);
@@ -1159,6 +1161,7 @@ void __lockfunc rt_spin_lock_nest_lock(spinlock_t *lock,
 {
 	spin_acquire_nest(&lock->dep_map, 0, 0, nest_lock, _RET_IP_);
 	rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
+	rcu_read_lock();
 	migrate_disable();
 }
 EXPORT_SYMBOL(rt_spin_lock_nest_lock);
@@ -1169,6 +1172,7 @@ void __lockfunc rt_spin_unlock(spinlock_t *lock)
 	/* NOTE: we always pass in '1' for nested, for simplicity */
 	spin_release(&lock->dep_map, _RET_IP_);
 	migrate_enable();
+	rcu_read_unlock();
 	rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock);
 }
 EXPORT_SYMBOL(rt_spin_unlock);
@@ -1198,6 +1202,7 @@ int __lockfunc rt_spin_trylock(spinlock_t *lock)
 	ret = __rt_mutex_trylock(&lock->lock);
 	if (ret) {
 		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+		rcu_read_lock();
 		migrate_disable();
 	}
 	return ret;
@@ -1212,6 +1217,7 @@ int __lockfunc rt_spin_trylock_bh(spinlock_t *lock)
 	ret = __rt_mutex_trylock(&lock->lock);
 	if (ret) {
 		spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+		rcu_read_lock();
 		migrate_disable();
 	} else {
 		local_bh_enable();
diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c
index 16be7111aae7..3d2d1f14b513 100644
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -270,6 +270,7 @@ int __lockfunc rt_read_trylock(rwlock_t *rwlock)
 	ret = __read_rt_trylock(rwlock);
 	if (ret) {
 		rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
+		rcu_read_lock();
 		migrate_disable();
 	}
 	return ret;
@@ -283,6 +284,7 @@ int __lockfunc rt_write_trylock(rwlock_t *rwlock)
 	ret = __write_rt_trylock(rwlock);
 	if (ret) {
 		rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
+		rcu_read_lock();
 		migrate_disable();
 	}
 	return ret;
@@ -293,6 +295,7 @@ void __lockfunc rt_read_lock(rwlock_t *rwlock)
 {
 	rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
 	__read_rt_lock(rwlock);
+	rcu_read_lock();
 	migrate_disable();
 }
 EXPORT_SYMBOL(rt_read_lock);
@@ -301,6 +304,7 @@ void __lockfunc rt_write_lock(rwlock_t *rwlock)
 {
 	rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
 	__write_rt_lock(rwlock);
+	rcu_read_lock();
 	migrate_disable();
 }
 EXPORT_SYMBOL(rt_write_lock);
@@ -309,6 +313,7 @@ void __lockfunc rt_read_unlock(rwlock_t *rwlock)
 {
 	rwlock_release(&rwlock->dep_map, _RET_IP_);
 	migrate_enable();
+	rcu_read_unlock();
 	__read_rt_unlock(rwlock);
 }
 EXPORT_SYMBOL(rt_read_unlock);
@@ -317,6 +322,7 @@ void __lockfunc rt_write_unlock(rwlock_t *rwlock)
 {
 	rwlock_release(&rwlock->dep_map, _RET_IP_);
 	migrate_enable();
+	rcu_read_unlock();
 	__write_rt_unlock(rwlock);
 }
 EXPORT_SYMBOL(rt_write_unlock);
-- 
2.49.0

