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Subject[RESEND PATCH 06/11] kernel:lockdep:introduce print_shortest_lock_dependencies
Date
From: Ming Lei <tom.leiming@gmail.com>

Since the shortest lock dependencies' path may be obtained by BFS,
we print the shortest one by print_shortest_lock_dependencies().

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
kernel/lockdep.c | 93 +++++++++++++++++++++++++++++++------------
kernel/lockdep_internals.h | 4 +-
2 files changed, 69 insertions(+), 28 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 94b2f1f..d839994 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -576,6 +576,36 @@ static void print_lock_class_header(struct lock_class *class, int depth)
}

/*
+ * printk the shortest lock dependencies from @start to @end in reverse order:
+ */
+static void __used
+print_shortest_lock_dependencies(struct lock_list *leaf,
+ struct lock_list *root)
+{
+ struct lock_list *entry = leaf;
+ int depth;
+
+ /*compute depth from generated tree by BFS*/
+ depth = get_lock_depth(leaf);
+
+ do {
+ print_lock_class_header(entry->class, depth);
+ printk("%*s ... acquired at:\n", depth, "");
+ print_stack_trace(&entry->trace, 2);
+ printk("\n");
+
+ if (depth == 0 && (entry != root)) {
+ printk("lockdep:%s bad BFS generated tree\n", __func__);
+ break;
+ }
+
+ entry = get_lock_parent(entry);
+ depth--;
+ } while (entry && (depth >= 0));
+
+ return;
+}
+/*
* printk all lock dependencies starting at <entry>:
*/
static void __used
@@ -992,7 +1022,7 @@ static inline int __bfs_backwards(struct lock_list *src_entry,
* has been detected):
*/
static noinline int
-print_circular_bug_entry(struct lock_list *target, unsigned int depth)
+print_circular_bug_entry(struct lock_list *target, int depth)
{
if (debug_locks_silent)
return 0;
@@ -1047,7 +1077,7 @@ static noinline int print_circular_bug(struct lock_list *this,
{
struct task_struct *curr = current;
struct lock_list *parent;
- unsigned long depth;
+ int depth;

if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;
@@ -1169,7 +1199,6 @@ 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 struct lock_class *forwards_match, *backwards_match;


#define BFS_PROCESS_RET(ret) do { \
@@ -1235,6 +1264,10 @@ find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,

static int
print_bad_irq_dependency(struct task_struct *curr,
+ struct lock_list *prev_root,
+ struct lock_list *next_root,
+ struct lock_list *backwards_entry,
+ struct lock_list *forwards_entry,
struct held_lock *prev,
struct held_lock *next,
enum lock_usage_bit bit1,
@@ -1267,26 +1300,32 @@ print_bad_irq_dependency(struct task_struct *curr,

printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
irqclass);
- print_lock_name(backwards_match);
+ print_lock_name(backwards_entry->class);
printk("\n... which became %s-irq-safe at:\n", irqclass);

- print_stack_trace(backwards_match->usage_traces + bit1, 1);
+ print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);

printk("\nto a %s-irq-unsafe lock:\n", irqclass);
- print_lock_name(forwards_match);
+ print_lock_name(forwards_entry->class);
printk("\n... which became %s-irq-unsafe at:\n", irqclass);
printk("...");

- print_stack_trace(forwards_match->usage_traces + bit2, 1);
+ print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);

printk("\nother info that might help us debug this:\n\n");
lockdep_print_held_locks(curr);

- printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
- print_lock_dependencies(backwards_match, 0);
+ printk("\nthe dependencies between %s-irq-safe lock", irqclass);
+ printk(" and the holding lock:\n");
+ if (!save_trace(&prev_root->trace))
+ return 0;
+ print_shortest_lock_dependencies(backwards_entry, prev_root);

- printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
- print_lock_dependencies(forwards_match, 0);
+ printk("\nthe dependencies between the lock to be acquired");
+ printk(" and %s-irq-unsafe lock:\n", irqclass);
+ if (!save_trace(&next_root->trace))
+ return 0;
+ print_shortest_lock_dependencies(forwards_entry, next_root);

printk("\nstack backtrace:\n");
dump_stack();
@@ -1300,22 +1339,24 @@ 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 this, that;
struct lock_list *uninitialized_var(target_entry);
+ struct lock_list *uninitialized_var(target_entry1);

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);
+ that.parent = NULL;
+ that.class = hlock_class(next);
+ ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
BFS_PROCESS_RET(ret);
- forwards_match = target_entry->class;

- return print_bad_irq_dependency(curr, prev, next,
+ return print_bad_irq_dependency(curr, &this, &that,
+ target_entry, target_entry1,
+ prev, next,
bit_backwards, bit_forwards, irqclass);
}

@@ -1944,7 +1985,8 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
* print irq inversion bug:
*/
static int
-print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
+print_irq_inversion_bug(struct task_struct *curr,
+ struct lock_list *root, struct lock_list *other,
struct held_lock *this, int forwards,
const char *irqclass)
{
@@ -1962,17 +2004,16 @@ print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
else
printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
- print_lock_name(other);
+ print_lock_name(other->class);
printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");

printk("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);

- printk("\nthe first lock's dependencies:\n");
- print_lock_dependencies(hlock_class(this), 0);
-
- printk("\nthe second lock's dependencies:\n");
- print_lock_dependencies(other, 0);
+ printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
+ if (!save_trace(&root->trace))
+ return 0;
+ print_shortest_lock_dependencies(other, root);

printk("\nstack backtrace:\n");
dump_stack();
@@ -1997,7 +2038,7 @@ check_usage_forwards(struct task_struct *curr, struct held_lock *this,
ret = find_usage_forwards(&root, bit, &target_entry);
BFS_PROCESS_RET(ret);

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

@@ -2018,7 +2059,7 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this,
ret = find_usage_backwards(&root, bit, &target_entry);
BFS_PROCESS_RET(ret);

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

diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index c2f6594..b115aaa 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -219,9 +219,9 @@ static inline struct lock_list *get_lock_parent(struct lock_list *child)
return child->parent;
}

-static inline unsigned long get_lock_depth(struct lock_list *child)
+static inline int get_lock_depth(struct lock_list *child)
{
- unsigned long depth = 0;
+ int depth = 0;
struct lock_list *parent;

while ((parent = get_lock_parent(child))) {
--
1.6.0.GIT


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