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Subject[PATCH RT 15/23] locking: Make spinlock_t and rwlock_t a RCU section on RT
Date
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

v4.14.170-rt75-rc2 stable review patch.
If anyone has any objections, please let me know.

-----------


[ Upstream commit 84440022a0e1c8c936d61f8f97593674a295d409 ]

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>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
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 4bc01a2a9a88..848d9ed6f053 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1142,6 +1142,7 @@ void __sched rt_spin_lock_slowunlock(struct rt_mutex *lock)
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);
@@ -1157,6 +1158,7 @@ void __lockfunc __rt_spin_lock(struct rt_mutex *lock)
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);
@@ -1170,6 +1172,7 @@ 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();
+ rcu_read_unlock();
sleeping_lock_dec();
}
EXPORT_SYMBOL(rt_spin_unlock);
@@ -1201,6 +1204,7 @@ 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();
} else {
migrate_enable();
sleeping_lock_dec();
@@ -1217,6 +1221,7 @@ int __lockfunc rt_spin_trylock_bh(spinlock_t *lock)
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
@@ -1233,6 +1238,7 @@ int __lockfunc rt_spin_trylock_irqsave(spinlock_t *lock, unsigned long *flags)
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_);
}
diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c
index c3b91205161c..0ae8c62ea832 100644
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -310,6 +310,7 @@ int __lockfunc rt_read_trylock(rwlock_t *rwlock)
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 *rwlock)
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)
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)
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);
--
2.14.1
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