[PATCH v4 05/15] lockdep: Make check_prev_add can use a separate stack_trace

Byungchul Park
2016-12-09T05:16:40Z

check_prev_add() saves a stack trace of the current. But crossrelease
feature needs to use a separate stack trace of another context in
check_prev_add(). So make it use a separate stack trace instead of one
of the current.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/locking/lockdep.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 111839f..3eaa11c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1793,7 +1793,8 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
*/
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, int *stack_saved,
+ struct stack_trace *own_trace)
{
struct lock_list *entry;
int ret;
@@ -1854,7 +1855,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
}
}

- if (!*stack_saved) {
+ if (!own_trace && stack_saved && !*stack_saved) {
if (!save_trace(&trace))
return 0;
*stack_saved = 1;
@@ -1866,14 +1867,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
*/
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, own_trace ?: &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, own_trace ?: &trace);
if (!ret)
return 0;

@@ -1882,7 +1883,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
*/
if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
/* We drop graph lock, so another thread can overwrite trace. */
- *stack_saved = 0;
+ if (stack_saved)
+ *stack_saved = 0;
graph_unlock();
printk("\n new dependency: ");
print_lock_name(hlock_class(prev));
@@ -1931,8 +1933,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
* added:
*/
if (hlock->read != 2 && hlock->check) {
- if (!check_prev_add(curr, hlock, next,
- distance, &stack_saved))
+ if (!check_prev_add(curr, hlock, next, distance,
+ &stack_saved, NULL))
return 0;
/*
* Stop after the first non-trylock entry,
--
1.9.1