[PATCH] locking/refcount: add sparse annotations to dec-and-lock functions

* [PATCH] locking/refcount: add sparse annotations to dec-and-lock functions
@ 2019-12-26 15:29 Eric Biggers
  2019-12-28 11:49 ` Peter Zijlstra
  0 siblings, 1 reply; 14+ messages in thread
From: Eric Biggers @ 2019-12-26 15:29 UTC (permalink / raw)
  To: linux-kernel, Ingo Molnar, Peter Zijlstra, Will Deacon
  Cc: Elena Reshetova, Thomas Gleixner, Kees Cook, Anna-Maria Gleixner,
	Sebastian Andrzej Siewior

From: Eric Biggers <ebiggers@google.com>

Wrap refcount_dec_and_lock() and refcount_dec_and_lock_irqsave() with
macros using __cond_lock() so that 'sparse' doesn't report warnings
about unbalanced locking when using them.

This is the same thing that's done for their atomic_t equivalents.

Don't annotate refcount_dec_and_mutex_lock(), because mutexes don't
currently have sparse annotations.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/linux/refcount.h | 45 ++++++++++++++++++++++++++++++++++++----
 lib/refcount.c           | 39 +++++-----------------------------
 2 files changed, 46 insertions(+), 38 deletions(-)

diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 0ac50cf62d06..6bb5ab9e98ed 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -300,8 +300,45 @@ static inline void refcount_dec(refcount_t *r)
 extern __must_check bool refcount_dec_if_one(refcount_t *r);
 extern __must_check bool refcount_dec_not_one(refcount_t *r);
 extern __must_check bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock);
-extern __must_check bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock);
-extern __must_check bool refcount_dec_and_lock_irqsave(refcount_t *r,
-						       spinlock_t *lock,
-						       unsigned long *flags);
+
+/**
+ * refcount_dec_and_lock - return holding spinlock if able to decrement
+ *                         refcount to 0
+ * @r: the refcount
+ * @lock: the spinlock to be locked
+ *
+ * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
+ * decrement when saturated at REFCOUNT_SATURATED.
+ *
+ * Provides release memory ordering, such that prior loads and stores are done
+ * before, and provides a control dependency such that free() must come after.
+ * See the comment on top.
+ *
+ * Return: true and hold spinlock if able to decrement refcount to 0, false
+ *         otherwise
+ */
+extern __must_check bool _refcount_dec_and_lock(refcount_t *r,
+						spinlock_t *lock);
+#define refcount_dec_and_lock(r, lock) \
+	__cond_lock(lock, _refcount_dec_and_lock(r, lock))
+
+/**
+ * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
+ *                                 interrupts if able to decrement refcount to 0
+ * @r: the refcount
+ * @lock: the spinlock to be locked
+ * @flags: saved IRQ-flags if the is acquired
+ *
+ * Same as refcount_dec_and_lock() above except that the spinlock is acquired
+ * with disabled interrupts.
+ *
+ * Return: true and hold spinlock if able to decrement refcount to 0, false
+ *         otherwise
+ */
+extern __must_check bool _refcount_dec_and_lock_irqsave(refcount_t *r,
+							spinlock_t *lock,
+							unsigned long *flags);
+#define refcount_dec_and_lock_irqsave(r, lock, flags) \
+	__cond_lock(lock, _refcount_dec_and_lock_irqsave(r, lock, flags))
+
 #endif /* _LINUX_REFCOUNT_H */
diff --git a/lib/refcount.c b/lib/refcount.c
index ebac8b7d15a7..f0eb996b28c0 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -125,23 +125,7 @@ bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
 }
 EXPORT_SYMBOL(refcount_dec_and_mutex_lock);
 
-/**
- * refcount_dec_and_lock - return holding spinlock if able to decrement
- *                         refcount to 0
- * @r: the refcount
- * @lock: the spinlock to be locked
- *
- * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
- * decrement when saturated at REFCOUNT_SATURATED.
- *
- * Provides release memory ordering, such that prior loads and stores are done
- * before, and provides a control dependency such that free() must come after.
- * See the comment on top.
- *
- * Return: true and hold spinlock if able to decrement refcount to 0, false
- *         otherwise
- */
-bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
+bool _refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
 {
 	if (refcount_dec_not_one(r))
 		return false;
@@ -154,23 +138,10 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
 
 	return true;
 }
-EXPORT_SYMBOL(refcount_dec_and_lock);
+EXPORT_SYMBOL(_refcount_dec_and_lock);
 
-/**
- * refcount_dec_and_lock_irqsave - return holding spinlock with disabled
- *                                 interrupts if able to decrement refcount to 0
- * @r: the refcount
- * @lock: the spinlock to be locked
- * @flags: saved IRQ-flags if the is acquired
- *
- * Same as refcount_dec_and_lock() above except that the spinlock is acquired
- * with disabled interupts.
- *
- * Return: true and hold spinlock if able to decrement refcount to 0, false
- *         otherwise
- */
-bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
-				   unsigned long *flags)
+bool _refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
+				    unsigned long *flags)
 {
 	if (refcount_dec_not_one(r))
 		return false;
@@ -183,4 +154,4 @@ bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock,
 
 	return true;
 }
-EXPORT_SYMBOL(refcount_dec_and_lock_irqsave);
+EXPORT_SYMBOL(_refcount_dec_and_lock_irqsave);
-- 
2.24.1


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