diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b25d1b53df0dfdefce12db40c2592b3cb1f0f546..9ec026f8d09eded9b32dfa6f3c8002d5d976d1c2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -149,6 +149,12 @@ struct lock_list {
struct lock_class *class;
struct stack_trace trace;
int distance;
+
+ /*The parent field is used to implement breadth-first search,and
+ *the bit 0 is reused to indicate if the lock has been accessed
+ *in BFS.
+ */
+ struct lock_list *parent;
};
/*
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 8bbeef996c76598b7e45e3b48186fc18c03b5be0..93dc70d18cdf0ea3128ddc1f6426b4d26cac7697 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -897,6 +897,79 @@ static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
return 1;
}
+static struct circular_queue lock_cq;
+static int __search_shortest_path(struct lock_list *source_entry,
+ struct lock_class *target,
+ struct lock_list **target_entry,
+ int forward)
+{
+ struct lock_list *entry;
+ struct circular_queue *cq = &lock_cq;
+ int ret = 1;
+
+ __cq_init(cq);
+
+ mark_lock_accessed(source_entry, NULL);
+ if (source_entry->class == target) {
+ *target_entry = source_entry;
+ ret = 0;
+ goto exit;
+ }
+
+ __cq_enqueue(cq, (unsigned long)source_entry);
+
+ while (!__cq_empty(cq)) {
+ struct lock_list *lock;
+ struct list_head *head;
+
+ __cq_dequeue(cq, (unsigned long *)&lock);
+
+ if (!lock->class) {
+ ret = -2;
+ goto exit;
+ }
+
+ if (forward)
+ head = &lock->class->locks_after;
+ else
+ head = &lock->class->locks_before;
+
+ list_for_each_entry(entry, head, entry) {
+ if (!lock_accessed(entry)) {
+ mark_lock_accessed(entry, lock);
+ if (entry->class == target) {
+ *target_entry = entry;
+ ret = 0;
+ goto exit;
+ }
+
+ if (__cq_enqueue(cq, (unsigned long)entry)) {
+ ret = -1;
+ goto exit;
+ }
+ }
+ }
+ }
+exit:
+ return ret;
+}
+
+static inline int __search_forward_shortest_path(struct lock_list *src_entry,
+ struct lock_class *target,
+ struct lock_list **target_entry)
+{
+ return __search_shortest_path(src_entry, target, target_entry, 1);
+
+}
+
+static inline int __search_backward_shortest_path(struct lock_list *src_entry,
+ struct lock_class *target,
+ struct lock_list **target_entry)
+{
+ return __search_shortest_path(src_entry, target, target_entry, 0);
+
+}
+
/*
* Recursive, forwards-direction lock-dependency checking, used for
* both noncyclic checking and for hardirq-unsafe/softirq-unsafe
@@ -934,7 +1007,7 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
{
struct task_struct *curr = current;
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+ if (debug_locks_silent)
return 0;
printk("\n=======================================================\n");
@@ -954,19 +1027,41 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth)
return 0;
}
-static noinline int print_circular_bug_tail(void)
+static noinline int print_circular_bug(void)
{
struct task_struct *curr = current;
struct lock_list this;
+ struct lock_list *target;
+ struct lock_list *parent;
+ int result;
+ unsigned long depth;
- if (debug_locks_silent)
+ if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;
this.class = hlock_class(check_source);
if (!save_trace(&this.trace))
return 0;
- print_circular_bug_entry(&this, 0);
+ result = __search_forward_shortest_path(&this,
+ hlock_class(check_target),
+ &target);
+ if (result) {
+ printk("\n%s:search shortest path failed:%d\n", __func__,
+ result);
+ return 0;
+ }
+
+ depth = get_lock_depth(target);
+
+ print_circular_bug_header(target, depth);
+
+ parent = get_lock_parent(target);
+
+ while (parent) {
+ print_circular_bug_entry(parent, --depth);
+ parent = get_lock_parent(parent);
+ }
printk("\nother info that might help us debug this:\n\n");
lockdep_print_held_locks(curr);
@@ -1072,14 +1167,15 @@ check_noncircular(struct lock_class *source, unsigned int depth)
*/
list_for_each_entry(entry, &source->locks_after, entry) {
if (entry->class == hlock_class(check_target))
- return print_circular_bug_header(entry, depth+1);
+ return 2;
debug_atomic_inc(&nr_cyclic_checks);
- if (!check_noncircular(entry->class, depth+1))
- return print_circular_bug_entry(entry, depth+1);
+ if (check_noncircular(entry->class, depth+1) == 2)
+ return 2;
}
return 1;
}
+
#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
/*
* Forwards and backwards subgraph searching, for the purposes of
@@ -1484,8 +1580,9 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
*/
check_source = next;
check_target = prev;
- if (!(check_noncircular(hlock_class(next), 0)))
- return print_circular_bug_tail();
+ if (check_noncircular(hlock_class(next), 0) == 2)
+ return print_circular_bug();
+
if (!check_prev_add_irq(curr, prev, next))
return 0;
diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index 699a2ac3a0d71c53476f5f0ba60436f40da8c58c..6f48d37d5be28feb1e54d216852a8dd340dbbb7c 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -136,3 +136,86 @@ extern atomic_t nr_find_usage_backwards_recursions;
# define debug_atomic_dec(ptr) do { } while (0)
# define debug_atomic_read(ptr) 0
#endif
+
+/* The circular_queue and helpers is used to implement the
+ * breadth-first search(BFS)algorithem, by which we can build
+ * the shortest path from the next lock to be acquired to the
+ * previous held lock if there is a circular between them.
+ * */
+#define MAX_CIRCULAR_QUE_SIZE 4096UL
+struct circular_queue{
+ unsigned long element[MAX_CIRCULAR_QUE_SIZE];
+ unsigned int front, rear;
+};
+
+#define LOCK_ACCESSED 1UL
+#define LOCK_ACCESSED_MASK (~LOCK_ACCESSED)
+
+static inline void __cq_init(struct circular_queue *cq)
+{
+ cq->front = cq->rear = 0;
+}
+
+static inline int __cq_empty(struct circular_queue *cq)
+{
+ return (cq->front == cq->rear);
+}
+
+static inline int __cq_full(struct circular_queue *cq)
+{
+ return ((cq->rear + 1)%MAX_CIRCULAR_QUE_SIZE) == cq->front;
+}
+
+static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
+{
+ if (__cq_full(cq))
+ return -1;
+
+ cq->element[cq->rear] = elem;
+ cq->rear = (cq->rear + 1)%MAX_CIRCULAR_QUE_SIZE;
+ return 0;
+}
+
+static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
+{
+ if (__cq_empty(cq))
+ return -1;
+
+ *elem = cq->element[cq->front];
+ cq->front = (cq->front + 1)%MAX_CIRCULAR_QUE_SIZE;
+ return 0;
+}
+
+static inline int __cq_get_elem_count(struct circular_queue *cq)
+{
+ return (cq->rear - cq->front)%MAX_CIRCULAR_QUE_SIZE;
+}
+
+static inline void mark_lock_accessed(struct lock_list *lock,
+ struct lock_list *parent)
+{
+ lock->parent = (void *) parent + LOCK_ACCESSED;
+}
+
+static inline unsigned long lock_accessed(struct lock_list *lock)
+{
+ return (unsigned long)lock->parent & LOCK_ACCESSED;
+}
+
+static inline struct lock_list *get_lock_parent(struct lock_list *child)
+{
+ return (struct lock_list *)
+ ((unsigned long)child->parent & LOCK_ACCESSED_MASK);
+}
+
+static inline unsigned long get_lock_depth(struct lock_list *child)
+{
+ unsigned long depth = 0;
+ struct lock_list *parent;
+
+ while ((parent = get_lock_parent(child))) {
+ child = parent;
+ depth++;
+ }
+ return depth;
+}