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

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1246201486-7308-6-git-send-email-tom.leiming@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Ming Lei authored and Peter Zijlstra committed Jul 24, 2009
1 parent db0002a commit d7aaba1
Showing 1 changed file with 72 additions and 108 deletions.
180 changes: 72 additions & 108 deletions kernel/lockdep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -963,7 +963,7 @@ static int __bfs(struct lock_list *source_entry,
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)
Expand All @@ -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)
Expand Down Expand Up @@ -1085,18 +1085,6 @@ static noinline int 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)
{
Expand Down Expand Up @@ -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;
}
Expand All @@ -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,
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
}

/*
Expand All @@ -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)
Expand Down

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