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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);
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