[PATCH] lockdep: Make a stack_trace instance passed to check_prev_add as an arg

Byungchul Park
2017-01-13T04:09:46Z

Like this. Right?

----->8-----
>From c6173f29ff9bf801649f3cbeb80a914fdf1b998b Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul.park@lge.com>
Date: Fri, 13 Jan 2017 12:02:02 +0900
Subject: [PATCH] lockdep: Make a stack_trace instance passed to check_prev_add
as an arg

Saving stack_trace within check_prev_add needs many tricky codes. To
avoid these, this patch makes the stack_trace instance created out of
check_prev_add, but by caller and passed as an argument.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/locking/lockdep.c | 30 +++++++++---------------------
1 file changed, 9 insertions(+), 21 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2081c31..049fc71 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1797,20 +1797,13 @@ static inline void inc_chains(void)
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next, int distance, int *stack_saved)
+ struct held_lock *next, int distance,
+ struct stack_trace *trace)
{
struct lock_list *entry;
int ret;
struct lock_list this;
struct lock_list *uninitialized_var(target_entry);
- /*
- * Static variable, serialized by the graph_lock().
- *
- * We use this static variable to save the stack trace in case
- * we call into this function multiple times due to encountering
- * trylocks in the held lock stack.
- */
- static struct stack_trace trace;

/*
* Prove that the new <prev> -> <next> dependency would not
@@ -1858,26 +1851,20 @@ static inline void inc_chains(void)
}
}

- if (!*stack_saved) {
- if (!save_trace(&trace))
- return 0;
- *stack_saved = 1;
- }
-
/*
* Ok, all validations passed, add the new lock
* to the previous lock's dependency list:
*/
ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
&hlock_class(prev)->locks_after,
- next->acquire_ip, distance, &trace);
+ next->acquire_ip, distance, trace);

if (!ret)
return 0;

ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
&hlock_class(next)->locks_before,
- next->acquire_ip, distance, &trace);
+ next->acquire_ip, distance, trace);
if (!ret)
return 0;

@@ -1885,8 +1872,6 @@ static inline void inc_chains(void)
* Debugging printouts:
*/
if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
- /* We drop graph lock, so another thread can overwrite trace. */
- *stack_saved = 0;
graph_unlock();
printk("\n new dependency: ");
print_lock_name(hlock_class(prev));
@@ -1909,8 +1894,8 @@ static inline void inc_chains(void)
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
int depth = curr->lockdep_depth;
- int stack_saved = 0;
struct held_lock *hlock;
+ struct stack_trace trace;

/*
* Debugging checks.
@@ -1927,6 +1912,9 @@ static inline void inc_chains(void)
curr->held_locks[depth-1].irq_context)
goto out_bug;

+ if (!save_trace(&trace))
+ return 0;
+
for (;;) {
int distance = curr->lockdep_depth - depth + 1;
hlock = curr->held_locks + depth - 1;
@@ -1936,7 +1924,7 @@ static inline void inc_chains(void)
*/
if (hlock->read != 2 && hlock->check) {
if (!check_prev_add(curr, hlock, next,
- distance, &stack_saved))
+ distance, &trace))
return 0;
/*
* Stop after the first non-trylock entry,
--
1.9.1