lockdep: add lock_class information to lock_chain and output it

It is based on x86/master branch of git-x86 tree, and has been tested
on x86_64 platform.

ChangeLog:

v2:

- Enclosing proc file system related code into CONFIG_PROVE_LOCKING.

- Fix nr_chain_hlocks update code.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 11 insertions, 5 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index a796f1f38ac5..7553a28b99cd 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1459,7 +1459,7 @@ out_bug:
 
 unsigned long nr_lock_chains;
 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
-atomic_t nr_chain_hlocks;
+int nr_chain_hlocks;
 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
 
 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
@@ -1481,7 +1481,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
 	struct list_head *hash_head = chainhashentry(chain_key);
 	struct lock_chain *chain;
 	struct held_lock *hlock_curr, *hlock_next;
-	int i, j, n;
+	int i, j, n, cn;
 
 	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
 		return 0;
@@ -1540,9 +1540,15 @@ cache_hit:
 	}
 	i++;
 	chain->depth = curr->lockdep_depth + 1 - i;
-	n = atomic_add_return(chain->depth, &nr_chain_hlocks);
-	if (unlikely(n < MAX_LOCKDEP_CHAIN_HLOCKS)) {
-		chain->base = n - chain->depth;
+	cn = nr_chain_hlocks;
+	while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
+		n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
+		if (n == cn)
+			break;
+		cn = n;
+	}
+	if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
+		chain->base = cn;
 		for (j = 0; j < chain->depth - 1; j++, i++) {
 			int lock_id = curr->held_locks[i].class - lock_classes;
 			chain_hlocks[chain->base + j] = lock_id;