locking/rtmutex: Add a lockdep assert to catch potential nested blocking

There used to be a BUG_ON(current->pi_blocked_on) in the lock acquisition
functions, but that vanished in one of the rtmutex overhauls.

Bring it back in form of a lockdep assert to catch code paths which take
rtmutex based locks with current::pi_blocked_on != NULL.

Reported-by: Crystal Wood <swood@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230908162254.999499-7-bigeasy@linutronix.de

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index a3fe05d..4a10e8c 100644 (file)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1784,6 +1784,8 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
 static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
                                           unsigned int state)
 {
+       lockdep_assert(!current->pi_blocked_on);
+
        if (likely(rt_mutex_try_acquire(lock)))
                return 0;
 

diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c
index c7258cb..34a5956 100644 (file)
--- a/kernel/locking/rwbase_rt.c
+++ b/kernel/locking/rwbase_rt.c
@@ -133,6 +133,8 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb,
 static __always_inline int rwbase_read_lock(struct rwbase_rt *rwb,
                                            unsigned int state)
 {
+       lockdep_assert(!current->pi_blocked_on);
+
        if (rwbase_read_trylock(rwb))
                return 0;
 

diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c
index 842037b..38e2924 100644 (file)
--- a/kernel/locking/spinlock_rt.c
+++ b/kernel/locking/spinlock_rt.c
@@ -37,6 +37,8 @@
 
 static __always_inline void rtlock_lock(struct rt_mutex_base *rtm)
 {
+       lockdep_assert(!current->pi_blocked_on);
+
        if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
                rtlock_slowlock(rtm);
 }