linux-kernel - [PATCH -tip] locking/mutex: Complain upon api misuse wrt interrupt context

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Message-Id: <20191025033634.3330-1-dave@stgolabs.net>
Date:   Thu, 24 Oct 2019 20:36:34 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     mingo@...nel.org
Cc:     peterz@...radead.org, dave@...olabs.net,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH -tip] locking/mutex: Complain upon api misuse wrt interrupt context

Sprinkle warning checks, under CONFIG_DEBUG_MUTEXES. 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 <dbueso@...e.de>
---
 kernel/locking/mutex.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 468a9b8422e3..7e9c316c646c 100644
--- 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);
-- 
2.16.4