locking/lockdep: Add a skip() function to __bfs()

Some __bfs() walks will have additional iteration constraints (beyond
the path being strong). Provide an additional function to allow
terminating graph walks.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b061e29..f50f026 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1672,6 +1672,7 @@ static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
 static enum bfs_result __bfs(struct lock_list *source_entry,
                             void *data,
                             bool (*match)(struct lock_list *entry, void *data),
+                            bool (*skip)(struct lock_list *entry, void *data),
                             struct lock_list **target_entry,
                             int offset)
 {
@@ -1732,7 +1733,12 @@ static enum bfs_result __bfs(struct lock_list *source_entry,
                /*
                 * Step 3: we haven't visited this and there is a strong
                 *         dependency path to this, so check with @match.
+                *         If @skip is provide and returns true, we skip this
+                *         lock (and any path this lock is in).
                 */
+               if (skip && skip(lock, data))
+                       continue;
+
                if (match(lock, data)) {
                        *target_entry = lock;
                        return BFS_RMATCH;
@@ -1775,9 +1781,10 @@ static inline enum bfs_result
 __bfs_forwards(struct lock_list *src_entry,
               void *data,
               bool (*match)(struct lock_list *entry, void *data),
+              bool (*skip)(struct lock_list *entry, void *data),
               struct lock_list **target_entry)
 {
-       return __bfs(src_entry, data, match, target_entry,
+       return __bfs(src_entry, data, match, skip, target_entry,
                     offsetof(struct lock_class, locks_after));
 
 }
@@ -1786,9 +1793,10 @@ static inline enum bfs_result
 __bfs_backwards(struct lock_list *src_entry,
                void *data,
                bool (*match)(struct lock_list *entry, void *data),
+              bool (*skip)(struct lock_list *entry, void *data),
                struct lock_list **target_entry)
 {
-       return __bfs(src_entry, data, match, target_entry,
+       return __bfs(src_entry, data, match, skip, target_entry,
                     offsetof(struct lock_class, locks_before));
 
 }
@@ -2019,7 +2027,7 @@ static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
        unsigned long  count = 0;
        struct lock_list *target_entry;
 
-       __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
+       __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
 
        return count;
 }
@@ -2044,7 +2052,7 @@ static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
        unsigned long  count = 0;
        struct lock_list *target_entry;
 
-       __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
+       __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
 
        return count;
 }
@@ -2072,11 +2080,12 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
 static noinline enum bfs_result
 check_path(struct held_lock *target, struct lock_list *src_entry,
           bool (*match)(struct lock_list *entry, void *data),
+          bool (*skip)(struct lock_list *entry, void *data),
           struct lock_list **target_entry)
 {
        enum bfs_result ret;
 
-       ret = __bfs_forwards(src_entry, target, match, target_entry);
+       ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
 
        if (unlikely(bfs_error(ret)))
                print_bfs_bug(ret);
@@ -2103,7 +2112,7 @@ check_noncircular(struct held_lock *src, struct held_lock *target,
 
        debug_atomic_inc(nr_cyclic_checks);
 
-       ret = check_path(target, &src_entry, hlock_conflict, &target_entry);
+       ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
 
        if (unlikely(ret == BFS_RMATCH)) {
                if (!*trace) {
@@ -2152,7 +2161,7 @@ check_redundant(struct held_lock *src, struct held_lock *target)
 
        debug_atomic_inc(nr_redundant_checks);
 
-       ret = check_path(target, &src_entry, hlock_equal, &target_entry);
+       ret = check_path(target, &src_entry, hlock_equal, NULL, &target_entry);
 
        if (ret == BFS_RMATCH)
                debug_atomic_inc(nr_redundant);
@@ -2246,7 +2255,7 @@ find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
 
        debug_atomic_inc(nr_find_usage_forwards_checks);
 
-       result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);
+       result = __bfs_forwards(root, &usage_mask, usage_match, NULL, target_entry);
 
        return result;
 }
@@ -2263,7 +2272,7 @@ find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
 
        debug_atomic_inc(nr_find_usage_backwards_checks);
 
-       result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);
+       result = __bfs_backwards(root, &usage_mask, usage_match, NULL, target_entry);
 
        return result;
 }
@@ -2628,7 +2637,7 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
         */
        bfs_init_rootb(&this, prev);
 
-       ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
+       ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL, NULL);
        if (bfs_error(ret)) {
                print_bfs_bug(ret);
                return 0;