locking/lockdep: Make check_prev_add() able to handle external stack_trace

Currently, a space for stack_trace is pinned in check_prev_add(), that
makes us not able to use external stack_trace. The simplest way to
achieve it is to pass an external stack_trace as an argument.

A more suitable solution is to pass a callback additionally along with
a stack_trace so that callers can decide the way to save or whether to
save. Actually crossrelease needs to do other than saving a stack_trace.
So pass a stack_trace and callback to handle it, to check_prev_add().

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-5-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 19 insertions, 21 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7cf02fab1725..841828ba35b9 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1824,20 +1824,13 @@ 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, struct stack_trace *trace,
+               int (*save)(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
@@ -1899,11 +1892,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
                 return print_bfs_bug(ret);
 
 
-        if (!*stack_saved) {
-                if (!save_trace(&trace))
-                        return 0;
-                *stack_saved = 1;
-        }
+        if (save && !save(trace))
+                return 0;
 
         /*
          * Ok, all validations passed, add the new lock
@@ -1911,14 +1901,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          */
         ret = add_lock_to_list(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(prev),
                                &hlock_class(next)->locks_before,
-                               next->acquire_ip, distance, &trace);
+                               next->acquire_ip, distance, trace);
         if (!ret)
                 return 0;
 
@@ -1926,8 +1916,6 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
          * 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));
@@ -1951,8 +1939,9 @@ static int
 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;
+        int (*save)(struct stack_trace *trace) = save_trace;
 
         /*
          * Debugging checks.
@@ -1977,9 +1966,18 @@ 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))
+                        int ret = check_prev_add(curr, hlock, next,
+                                                distance, &trace, save);
+                        if (!ret)
                                 return 0;
+
+                        /*
+                         * Stop saving stack_trace if save_trace() was
+                         * called at least once:
+                         */
+                        if (save && ret == 2)
+                                save = NULL;
+
                         /*
                          * Stop after the first non-trylock entry,
                          * as non-trylock entries have added their