From: Sebastian Andrzej Siewior Date: Tue, 19 Nov 2019 09:25:04 +0100 Subject: [PATCH 310/342] locking: Make spinlock_t and rwlock_t a RCU section on RT Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=5a4cb6344d94ce566d562e036d4fd69ead0338f3 [ 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 Signed-off-by: Steven Rostedt (VMware) --- 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 dc95a81ae3a6..fe5153fc7665 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);