locking/lockdep: Fix lock used or unused stats error

The stats variable nr_unused_locks is incremented every time a new lock
class is register and decremented when the lock is first used in
__lock_acquire(). And after all, it is shown and checked in lockdep_stats.

However, under configurations that either CONFIG_TRACE_IRQFLAGS or
CONFIG_PROVE_LOCKING is not defined:

The commit:

  0918065 ("locking/lockdep: Consolidate lock usage bit initialization")

missed marking the LOCK_USED flag at IRQ usage initialization because
as mark_usage() is not called. And the commit:

  886532a ("locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING")

further made mark_lock() not defined such that the LOCK_USED cannot be
marked at all when the lock is first acquired.

As a result, we fix this by not showing and checking the stats under such
configurations for lockdep_stats.

Reported-by: Qian Cai <[email protected]>
Signed-off-by: Yuyang Du <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

kernel/locking/lockdep_proc.c

@@ -210,6 +210,7 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
 		      nr_hardirq_read_safe = 0, nr_hardirq_read_unsafe = 0,
 		      sum_forward_deps = 0;
 
+#ifdef CONFIG_PROVE_LOCKING
 	list_for_each_entry(class, &all_lock_classes, lock_entry) {
 
 		if (class->usage_mask == 0)
@@ -241,12 +242,12 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
 		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ_READ)
 			nr_hardirq_read_unsafe++;
 
-#ifdef CONFIG_PROVE_LOCKING
 		sum_forward_deps += lockdep_count_forward_deps(class);
-#endif
 	}
 #ifdef CONFIG_DEBUG_LOCKDEP
 	DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused);
+#endif
+
 #endif
 	seq_printf(m, " lock-classes:                  %11lu [max: %lu]\n",
 			nr_lock_classes, MAX_LOCKDEP_KEYS);