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Subject[PATCH 20/28] locking/lockdep: Refactorize check_noncircular and check_redundant
Date
These two functions now handle different check results themselves. A new
check_path function is added to check whether there is a path in the
dependency graph. No functional change.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
kernel/locking/lockdep.c | 98 +++++++++++++++++++++++++++++++-----------------
1 file changed, 63 insertions(+), 35 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a3138c9..4d42124 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1681,33 +1681,79 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
}

/*
- * Prove that the dependency graph starting at <entry> can not
- * lead to <target>. Print an error and return 0 if it does.
+ * Check that the dependency graph starting at <src> can lead to
+ * <target> or not. Print an error and return 0 if it does.
*/
static noinline int
-check_noncircular(struct lock_list *root, struct lock_class *target,
- struct lock_list **target_entry)
+check_path(struct lock_class *target, struct lock_list *src_entry,
+ struct lock_list **target_entry)
{
- int result;
+ int ret;
+
+ ret = __bfs_forwards(src_entry, (void *)target, class_equal,
+ target_entry);
+
+ if (unlikely(ret < 0))
+ print_bfs_bug(ret);
+
+ return ret;
+}
+
+/*
+ * Prove that the dependency graph starting at <src> can not
+ * lead to <target>. If it can, there is a circle when adding
+ * <target> -> <src> dependency.
+ *
+ * Print an error and return 0 if it does.
+ */
+static noinline int
+check_noncircular(struct held_lock *src, struct held_lock *target)
+{
+ int ret;
+ struct lock_list *uninitialized_var(target_entry);
+ struct lock_list src_entry = {
+ .class = hlock_class(src),
+ .parent = NULL,
+ };

debug_atomic_inc(nr_cyclic_checks);

- result = __bfs_forwards(root, target, class_equal, target_entry);
+ ret = check_path(hlock_class(target), &src_entry, &target_entry);

- return result;
+ if (unlikely(!ret))
+ print_circular_bug(&src_entry, target_entry, src, target);
+
+ return ret;
}

+/*
+ * Check that the dependency graph starting at <src> can lead to
+ * <target> or not. If it can, <src> -> <target> dependency is already
+ * in the graph.
+ *
+ * Print an error and return 2 if it does or 1 if it does not.
+ */
static noinline int
-check_redundant(struct lock_list *root, struct lock_class *target,
- struct lock_list **target_entry)
+check_redundant(struct held_lock *src, struct held_lock *target)
{
- int result;
+ int ret;
+ struct lock_list *uninitialized_var(target_entry);
+ struct lock_list src_entry = {
+ .class = hlock_class(src),
+ .parent = NULL,
+ };

debug_atomic_inc(nr_redundant_checks);

- result = __bfs_forwards(root, target, class_equal, target_entry);
+ ret = check_path(hlock_class(target), &src_entry, &target_entry);

- return result;
+ if (!ret) {
+ debug_atomic_inc(nr_redundant);
+ ret = 2;
+ } else if (ret < 0)
+ ret = 0;
+
+ return ret;
}

#if defined(CONFIG_TRACE_IRQFLAGS)
@@ -2208,9 +2254,7 @@ static inline void inc_chains(void)
check_prev_add(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next, int distance)
{
- struct lock_list *uninitialized_var(target_entry);
struct lock_list *entry;
- struct lock_list this;
struct lock_trace trace;
int ret;

@@ -2242,17 +2286,9 @@ static inline void inc_chains(void)
* MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
* in the graph whose neighbours are to be checked.
*/
- this.class = hlock_class(next);
- this.parent = NULL;
- ret = check_noncircular(&this, hlock_class(prev), &target_entry);
- if (unlikely(!ret)) {
- print_circular_bug(&this, target_entry, next, prev);
- return 0;
- }
- else if (unlikely(ret < 0)) {
- print_bfs_bug(ret);
+ ret = check_noncircular(next, prev);
+ if (unlikely(ret <= 0))
return 0;
- }

if (!check_prev_add_irq(curr, prev, next))
return 0;
@@ -2286,17 +2322,9 @@ static inline void inc_chains(void)
/*
* Is the <prev> -> <next> link redundant?
*/
- this.class = hlock_class(prev);
- this.parent = NULL;
- ret = check_redundant(&this, hlock_class(next), &target_entry);
- if (!ret) {
- debug_atomic_inc(nr_redundant);
- return 2;
- }
- if (ret < 0) {
- print_bfs_bug(ret);
- return 0;
- }
+ ret = check_redundant(prev, next);
+ if (ret != 1)
+ return ret;

if (!save_trace(&trace))
return 0;
--
1.8.3.1
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