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Subject[PATCH 4/8] kernel:lockdep:implement find_usage_*wards by BFS
Date
From: Ming Lei <tom.leiming@gmail.com>

This patch uses BFS to implement find_usage_*wards(),which
was originally writen by DFS.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
kernel/lockdep.c | 180 ++++++++++++++++++++++--------------------------------
1 files changed, 72 insertions(+), 108 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index f740088..94b2f1f 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -963,7 +963,7 @@ exit:
return ret;
}

-static inline int __bfs_forward(struct lock_list *src_entry,
+static inline int __bfs_forwards(struct lock_list *src_entry,
void *data,
int (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
@@ -972,7 +972,7 @@ static inline int __bfs_forward(struct lock_list *src_entry,

}

-static inline int __bfs_backward(struct lock_list *src_entry,
+static inline int __bfs_backwards(struct lock_list *src_entry,
void *data,
int (*match)(struct lock_list *entry, void *data),
struct lock_list **target_entry)
@@ -1085,18 +1085,6 @@ static int noinline print_bfs_bug(int ret)
return 0;
}

-#define RECURSION_LIMIT 40
-
-static int noinline print_infinite_recursion_bug(void)
-{
- if (!debug_locks_off_graph_unlock())
- return 0;
-
- WARN_ON(1);
-
- return 0;
-}
-
unsigned long __lockdep_count_forward_deps(struct lock_class *class,
unsigned int depth)
{
@@ -1170,7 +1158,7 @@ check_noncircular(struct lock_list *root, struct lock_class *target,

debug_atomic_inc(&nr_cyclic_checks);

- result = __bfs_forward(root, target, class_equal, target_entry);
+ result = __bfs_forwards(root, target, class_equal, target_entry);

return result;
}
@@ -1181,101 +1169,70 @@ check_noncircular(struct lock_list *root, struct lock_class *target,
* proving that two subgraphs can be connected by a new dependency
* without creating any illegal irq-safe -> irq-unsafe lock dependency.
*/
-static enum lock_usage_bit find_usage_bit;
static struct lock_class *forwards_match, *backwards_match;

+
+#define BFS_PROCESS_RET(ret) do { \
+ if (ret < 0) \
+ return print_bfs_bug(ret); \
+ if (ret == 1) \
+ return 1; \
+ } while (0)
+
+static inline int usage_match(struct lock_list *entry, void *bit)
+{
+ return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
+}
+
+
+
/*
* Find a node in the forwards-direction dependency sub-graph starting
- * at <source> that matches <find_usage_bit>.
+ * at @root->class that matches @bit.
*
- * Return 2 if such a node exists in the subgraph, and put that node
- * into <forwards_match>.
+ * Return 0 if such a node exists in the subgraph, and put that node
+ * into *@target_entry.
*
- * Return 1 otherwise and keep <forwards_match> unchanged.
- * Return 0 on error.
+ * Return 1 otherwise and keep *@target_entry unchanged.
+ * Return <0 on error.
*/
-static noinline int
-find_usage_forwards(struct lock_class *source, unsigned int depth)
+static int
+find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
+ struct lock_list **target_entry)
{
- struct lock_list *entry;
- int ret;
-
- if (lockdep_dependency_visit(source, depth))
- return 1;
-
- if (depth > max_recursion_depth)
- max_recursion_depth = depth;
- if (depth >= RECURSION_LIMIT)
- return print_infinite_recursion_bug();
+ int result;

debug_atomic_inc(&nr_find_usage_forwards_checks);
- if (source->usage_mask & (1 << find_usage_bit)) {
- forwards_match = source;
- return 2;
- }

- /*
- * Check this lock's dependency list:
- */
- list_for_each_entry(entry, &source->locks_after, entry) {
- debug_atomic_inc(&nr_find_usage_forwards_recursions);
- ret = find_usage_forwards(entry->class, depth+1);
- if (ret == 2 || ret == 0)
- return ret;
- }
- return 1;
+ result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
+
+ return result;
}

/*
* Find a node in the backwards-direction dependency sub-graph starting
- * at <source> that matches <find_usage_bit>.
+ * at @root->class that matches @bit.
*
- * Return 2 if such a node exists in the subgraph, and put that node
- * into <backwards_match>.
+ * Return 0 if such a node exists in the subgraph, and put that node
+ * into *@target_entry.
*
- * Return 1 otherwise and keep <backwards_match> unchanged.
- * Return 0 on error.
+ * Return 1 otherwise and keep *@target_entry unchanged.
+ * Return <0 on error.
*/
-static noinline int
-find_usage_backwards(struct lock_class *source, unsigned int depth)
+static int
+find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
+ struct lock_list **target_entry)
{
- struct lock_list *entry;
- int ret;
-
- if (lockdep_dependency_visit(source, depth))
- return 1;
-
- if (!__raw_spin_is_locked(&lockdep_lock))
- return DEBUG_LOCKS_WARN_ON(1);
-
- if (depth > max_recursion_depth)
- max_recursion_depth = depth;
- if (depth >= RECURSION_LIMIT)
- return print_infinite_recursion_bug();
+ int result;

debug_atomic_inc(&nr_find_usage_backwards_checks);
- if (source->usage_mask & (1 << find_usage_bit)) {
- backwards_match = source;
- return 2;
- }

- if (!source && debug_locks_off_graph_unlock()) {
- WARN_ON(1);
- return 0;
- }
+ result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);

- /*
- * Check this lock's dependency list:
- */
- list_for_each_entry(entry, &source->locks_before, entry) {
- debug_atomic_inc(&nr_find_usage_backwards_recursions);
- ret = find_usage_backwards(entry->class, depth+1);
- if (ret == 2 || ret == 0)
- return ret;
- }
- return 1;
+ return result;
}

+
static int
print_bad_irq_dependency(struct task_struct *curr,
struct held_lock *prev,
@@ -1343,18 +1300,21 @@ check_usage(struct task_struct *curr, struct held_lock *prev,
enum lock_usage_bit bit_forwards, const char *irqclass)
{
int ret;
+ struct lock_list this;
+ struct lock_list *uninitialized_var(target_entry);
+
+ this.parent = NULL;
+
+ this.class = hlock_class(prev);
+ ret = find_usage_backwards(&this, bit_backwards, &target_entry);
+ BFS_PROCESS_RET(ret);
+ backwards_match = target_entry->class;
+
+ this.class = hlock_class(next);
+ ret = find_usage_forwards(&this, bit_forwards, &target_entry);
+ BFS_PROCESS_RET(ret);
+ forwards_match = target_entry->class;

- find_usage_bit = bit_backwards;
- /* fills in <backwards_match> */
- ret = find_usage_backwards(hlock_class(prev), 0);
- if (!ret || ret == 1)
- return ret;
-
- find_usage_bit = bit_forwards;
- ret = find_usage_forwards(hlock_class(next), 0);
- if (!ret || ret == 1)
- return ret;
- /* ret == 2 */
return print_bad_irq_dependency(curr, prev, next,
bit_backwards, bit_forwards, irqclass);
}
@@ -2029,14 +1989,16 @@ check_usage_forwards(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit bit, const char *irqclass)
{
int ret;
+ struct lock_list root;
+ struct lock_list *uninitialized_var(target_entry);

- find_usage_bit = bit;
- /* fills in <forwards_match> */
- ret = find_usage_forwards(hlock_class(this), 0);
- if (!ret || ret == 1)
- return ret;
+ root.parent = NULL;
+ root.class = hlock_class(this);
+ ret = find_usage_forwards(&root, bit, &target_entry);
+ BFS_PROCESS_RET(ret);

- return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
+ return print_irq_inversion_bug(curr, target_entry->class,
+ this, 1, irqclass);
}

/*
@@ -2048,14 +2010,16 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit bit, const char *irqclass)
{
int ret;
+ struct lock_list root;
+ struct lock_list *uninitialized_var(target_entry);

- find_usage_bit = bit;
- /* fills in <backwards_match> */
- ret = find_usage_backwards(hlock_class(this), 0);
- if (!ret || ret == 1)
- return ret;
+ root.parent = NULL;
+ root.class = hlock_class(this);
+ ret = find_usage_backwards(&root, bit, &target_entry);
+ BFS_PROCESS_RET(ret);

- return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
+ return print_irq_inversion_bug(curr, target_entry->class,
+ this, 1, irqclass);
}

void print_irqtrace_events(struct task_struct *curr)
--
1.6.0.GIT


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