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

Byungchul Park
2017-01-13T04:38:29Z

On Fri, Jan 13, 2017 at 01:09:41PM +0900, Byungchul Park wrote:
> Like this. Right?

Ignore this. We need to make save_trace work in different way first.

>
> ----->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