locking/mutex: Complain upon mutex API misuse in IRQ contexts

Add warning checks if mutex_trylock() or mutex_unlock() are used in
IRQ contexts, under CONFIG_DEBUG_MUTEXES=y.

While the mutex rules and semantics are explicitly documented, this allows
to expose any abusers and robustifies the whole thing.

While trylock and unlock are non-blocking, calling from IRQ context
is still forbidden (lock must be within the same context as unlock).

Signed-off-by: Davidlohr Bueso <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5352ce50a97e309b5bf8cdd2059378b17a8f14ec..54cc5f9286e93ee708fea396651ff3f53d1dbb1a 100644 (file)
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -733,6 +733,9 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
  */
 void __sched mutex_unlock(struct mutex *lock)
 {
+#ifdef CONFIG_DEBUG_MUTEXES
+       WARN_ON(in_interrupt());
+#endif
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
        if (__mutex_unlock_fast(lock))
                return;
@@ -1413,6 +1416,7 @@ int __sched mutex_trylock(struct mutex *lock)
 
 #ifdef CONFIG_DEBUG_MUTEXES
        DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+       WARN_ON(in_interrupt());
 #endif
 
        locked = __mutex_trylock(lock);