add_chain_cache() should be used in the context where the hlock is
owned since it might be racy in another context. However crossrelease
feature needs to build a chain between two locks regardless of context.
So introduce a new function making it possible.
Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
---
kernel/locking/lockdep.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 5df56aa..111839f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2105,6 +2105,62 @@ static int check_no_collision(struct task_struct *curr,
return 1;
}
+/*
+ * This is for building a chain between just two different classes,
+ * instead of adding a new hlock upon current, which is done by
+ * add_chain_cache().
+ *
+ * This can be called in any context with two classes, while
+ * add_chain_cache() must be done within the lock owener's context
+ * since it uses hlock which might be racy in another context.
+ */
+static inline int add_chain_cache_classes(unsigned int prev,
+ unsigned int next,
+ unsigned int irq_context,
+ u64 chain_key)
+{
+ struct hlist_head *hash_head = chainhashentry(chain_key);
+ struct lock_chain *chain;
+
+ /*
+ * Allocate a new chain entry from the static array, and add
+ * it to the hash:
+ */
+
+ /*
+ * We might need to take the graph lock, ensure we've got IRQs
+ * disabled to make this an IRQ-safe lock.. for recursion reasons
+ * lockdep won't complain about its own locking errors.
+ */
+ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+ return 0;
+
+ if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+ if (!debug_locks_off_graph_unlock())
+ return 0;
+
+ print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
+ dump_stack();
+ return 0;
+ }
+
+ chain = lock_chains + nr_lock_chains++;
+ chain->chain_key = chain_key;
+ chain->irq_context = irq_context;
+ chain->depth = 2;
+ if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
+ chain->base = nr_chain_hlocks;
+ nr_chain_hlocks += chain->depth;
+ chain_hlocks[chain->base] = prev - 1;
+ chain_hlocks[chain->base + 1] = next -1;
+ }
+ hlist_add_head_rcu(&chain->entry, hash_head);
+ debug_atomic_inc(chain_lookup_misses);
+ inc_chains();
+
+ return 1;
+}
+
static inline int add_chain_cache(struct task_struct *curr,
struct held_lock *hlock,
u64 chain_key)
--
1.9.1
--
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