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:

  091806515124b20 ("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:

  886532aee3cd42d ("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 <cai@lca.pw>
Signed-off-by: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: arnd@arndb.de
Cc: frederic@kernel.org
Link: https://lkml.kernel.org/r/20190709101522.9117-1-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 9c49ec645d8b5037e66d991f6b4dc2fa22d1c5fe..65b6a1600c8fd719ced51056093721f7c93b94c3 100644 (file)
--- a/kernel/locking/lockdep_proc.c
+++ b/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);