[PATCH v3 26/30] locking/lockdep: Add lock exclusiveness table

[Yuyang Du]

Lock exclusiveness table gathers the information about whether two lock
acquisitions for the same lock instance can be granted concurrently.

Signed-off-by: Yuyang Du <duyuyang@xxxxxxxxx>
---
 kernel/locking/lockdep.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index cb3a1d3..e11ffab 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -894,6 +894,36 @@ static bool class_lock_list_valid(struct lock_class *c, int forward)
 #ifdef CONFIG_PROVE_LOCKING
 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
 static u16 chain_hlocks_type[MAX_LOCKDEP_CHAIN_HLOCKS];
+
+/*
+ * Lock exclusiveness table.
+ *
+ * With lock X.A and X.B (X.A is on top and X.B is on bottom):
+ *
+ *   T1        TB                        T1        TB
+ *   --        --                        --        --
+ *
+ *   X.A                   or                      X.A
+ *             X.B                       X.B
+ *
+ * in the table Yes means the two locks are exclusive and No otherwise.
+ *
+ * +---------------------+------------+-----------+---------------------+
+ * |     X.A vs. X.B     | Write lock | Read lock | Recursive-read lock |
+ * +---------------------+------------+-----------+---------------------+
+ * |      Write lock     |     Yes    |    Yes    |         Yes         |
+ * +---------------------+------------+-----------+---------------------+
+ * |      Read lock      |     Yes    |    Yes    |         No          |
+ * +---------------------+------------+-----------+---------------------+
+ * | Recursive-read lock |     Yes    |    Yes    |         No          |
+ * +---------------------+------------+-----------+---------------------+
+ *
+ */
+static int lock_excl_table[3][3] = {
+	{1, 1, 1},	/* Write lock vs. X.B */
+	{1, 1, 0},	/* Read lock vs. X.B */
+	{1, 1, 0},	/* Recursive-read lock vs. X.B */
+};
 #endif
 
 static bool check_lock_chain_key(struct lock_chain *chain)
-- 
1.8.3.1