Commit-ID: 49347a986ab45eb1dafbf25170647c890f8ff192
Gitweb: http://git.kernel.org/tip/49347a986ab45eb1dafbf25170647c890f8ff192
Author: Byungchul Park <byungchul.park@xxxxxxx>
AuthorDate: Mon, 7 Aug 2017 16:12:49 +0900
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 10 Aug 2017 12:29:05 +0200
locking/lockdep: Add a function building a chain between two classes
Crossrelease needs to build a chain between two classes regardless of
their contexts. However, add_chain_cache() cannot be used for that
purpose since it assumes that it's called in the acquisition context
of the hlock. So this patch introduces a new function doing it.
Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: boqun.feng@xxxxxxxxx
Cc: kernel-team@xxxxxxx
Cc: kirill@xxxxxxxxxxxxx
Cc: npiggin@xxxxxxxxx
Cc: walken@xxxxxxxxxx
Cc: willy@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1502089981-21272-3-git-send-email-byungchul.park@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/locking/lockdep.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e029f2f..bdf6b31 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2151,6 +2151,76 @@ static int check_no_collision(struct task_struct *curr,
}
/*
+ * 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;
+ }
+#ifdef CONFIG_DEBUG_LOCKDEP
+ /*
+ * Important for check_no_collision().
+ */
+ else {
+ if (!debug_locks_off_graph_unlock())
+ return 0;
+
+ print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
+ dump_stack();
+ return 0;
+ }
+#endif
+
+ hlist_add_head_rcu(&chain->entry, hash_head);
+ debug_atomic_inc(chain_lookup_misses);
+ inc_chains();
+
+ return 1;
+}
+
+/*
* Adds a dependency chain into chain hashtable. And must be called with
* graph_lock held.
*
--
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