Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Ingo Molnar:
 "Two lockdep fixes for bugs introduced by the cross-release dependency
  tracking feature - plus a commit that disables it because performance
  regressed in an absymal fashion on some systems"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Disable cross-release features for now
  locking/selftest: Avoid false BUG report
  locking/lockdep: Fix stacktrace mess

1 files changed, 20 insertions, 28 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 44c8d0d17170..e36e652d996f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1873,10 +1873,10 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
                struct held_lock *next, int distance, struct stack_trace *trace,
                int (*save)(struct stack_trace *trace))
 {
+        struct lock_list *uninitialized_var(target_entry);
         struct lock_list *entry;
-        int ret;
         struct lock_list this;
-        struct lock_list *uninitialized_var(target_entry);
+        int ret;
 
         /*
          * Prove that the new <prev> -> <next> dependency would not
@@ -1890,8 +1890,17 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
         this.class = hlock_class(next);
         this.parent = NULL;
         ret = check_noncircular(&this, hlock_class(prev), &target_entry);
-        if (unlikely(!ret))
+        if (unlikely(!ret)) {
+                if (!trace->entries) {
+                        /*
+                         * If @save fails here, the printing might trigger
+                         * a WARN but because of the !nr_entries it should
+                         * not do bad things.
+                         */
+                        save(trace);
+                }
                 return print_circular_bug(&this, target_entry, next, prev, trace);
+        }
         else if (unlikely(ret < 0))
                 return print_bfs_bug(ret);
 
@@ -1938,7 +1947,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
                 return print_bfs_bug(ret);
 
 
-        if (save && !save(trace))
+        if (!trace->entries && !save(trace))
                 return 0;
 
         /*
@@ -1958,20 +1967,6 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
         if (!ret)
                 return 0;
 
-        /*
-         * Debugging printouts:
-         */
-        if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
-                graph_unlock();
-                printk("\n new dependency: ");
-                print_lock_name(hlock_class(prev));
-                printk(KERN_CONT " => ");
-                print_lock_name(hlock_class(next));
-                printk(KERN_CONT "\n");
-                dump_stack();
-                if (!graph_lock())
-                        return 0;
-        }
         return 2;
 }
 
@@ -1986,8 +1981,12 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
 {
         int depth = curr->lockdep_depth;
         struct held_lock *hlock;
-        struct stack_trace trace;
-        int (*save)(struct stack_trace *trace) = save_trace;
+        struct stack_trace trace = {
+                .nr_entries = 0,
+                .max_entries = 0,
+                .entries = NULL,
+                .skip = 0,
+        };
 
         /*
          * Debugging checks.
@@ -2018,18 +2017,11 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
                          */
                         if (hlock->read != 2 && hlock->check) {
                                 int ret = check_prev_add(curr, hlock, next,
-                                                         distance, &trace, save);
+                                                         distance, &trace, save_trace);
                                 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
                                  * own direct dependencies already, so this