[RFC 03/12] lockdep: Make check_prev_add can use a stack_trace of other context

From: Byungchul Park
Date: Mon Jun 20 2016 - 01:13:32 EST


Currently, check_prev_add() can only save its current context's stack
trace. But it would be useful if a seperated stack_trace can be taken
and used in check_prev_add(). Crossrelease feature can use
check_prev_add() with another context's stack_trace.

Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
---
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 4d51208..c596bef 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1822,7 +1822,8 @@ 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;
@@ -1883,7 +1884,7 @@ 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;
@@ -1895,14 +1896,14 @@ 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;

@@ -1911,7 +1912,8 @@ 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));
@@ -1960,8 +1962,8 @@ 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