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Subject[PATCH v4 20/30] locking/lockdep: Update direct dependency's read-write type if it exists
Date
When adding a dependency, if the dependency exists the dependency's
read-write type will be "upgraded" if the new dependency has more
exclusive lock types. The order toward more exclusiveness is:

recursive read -> read -> write.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
kernel/locking/lockdep.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 41cb735..eb88314 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1588,6 +1588,21 @@ static inline int get_lock_type2(struct lock_list *lock)
return lock->lock_type2;
}

+static inline int hlock_type(struct held_lock *hlock)
+{
+ return hlock->read;
+}
+
+static inline void set_lock_type1(struct lock_list *lock, int read)
+{
+ lock->lock_type1 = read;
+}
+
+static inline void set_lock_type2(struct lock_list *lock, int read)
+{
+ lock->lock_type2 = read;
+}
+
/*
* Forward- or backward-dependency search, used for both circular dependency
* checking and hardirq-unsafe/softirq-unsafe checking.
@@ -2585,6 +2600,17 @@ static inline void inc_chains(void)
list_add_tail_rcu(&chain->chain_entry, &entry->chains);
__set_bit(chain - lock_chains, lock_chains_in_dep);

+ /*
+ * For a direct dependency, smaller type value
+ * generally means more lock exlusiveness; we
+ * keep the more exlusive one, in other words,
+ * we "upgrade" the dependency if we can.
+ */
+ if (prev->read < get_lock_type1(entry))
+ set_lock_type1(entry, prev->read);
+ if (next->read < get_lock_type2(entry))
+ set_lock_type2(entry, next->read);
+
if (distance == 1)
entry->distance = 1;

--
1.8.3.1
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