linux-kernel - [PATCH 02/17] locking: Add split

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Message-Id: <20210409025131.4114078-3-willy@infradead.org>
Date:   Fri,  9 Apr 2021 03:51:16 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     neilb@...e.de, peterz@...radead.org, mingo@...hat.com,
        will@...nel.org, longman@...hat.com, boqun.feng@...il.com,
        tglx@...utronix.de, bigeasy@...utronix.de
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 02/17] locking: Add split_lock

Bitlocks do not currently participate in lockdep.  Conceptually, a
bit_spinlock is a split lock, eg across each bucket in a hash table.
The struct split_lock gives us somewhere to record the lockdep_map.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/split_lock.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 include/linux/split_lock.h

diff --git a/include/linux/split_lock.h b/include/linux/split_lock.h
new file mode 100644
index 000000000000..8d64cfa0bbad
--- /dev/null
+++ b/include/linux/split_lock.h
@@ -0,0 +1,37 @@
+#ifndef _LINUX_SPLIT_LOCK_H
+#define _LINUX_SPLIT_LOCK_H
+
+#include <linux/lockdep_types.h>
+
+struct split_lock {
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map dep_map;
+#endif
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define SPLIT_DEP_MAP_INIT(lockname)					\
+	.dep_map = {							\
+		.name = #lockname,					\
+		.wait_type_inner = LD_WAIT_SPIN,			\
+	}
+#else
+#define SPLIT_DEP_MAP_INIT(lockname)
+#endif
+
+#define DEFINE_SPLIT_LOCK(name)						\
+struct split_lock name = {						\
+	SPLIT_DEP_MAP_INIT(name)					\
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define split_lock_init(_lock) do {					\
+	static struct lock_class_key __key;				\
+	lockdep_init_map_wait(&(_lock)->dep_map, #_lock, &__key, 0,	\
+				LD_WAIT_SPIN);				\
+} while (0)
+#else
+static inline void split_lock_init(struct split_lock *sl) { }
+#endif
+
+#endif /* _LINUX_SPLIT_LOCK_H */
-- 
2.30.2