[PATCH v16 27/42] locking/lockdep: prevent various lockdep assertions when lockdep_off()'ed

[Byungchul Park]

lockdep provides APIs for assertion only if lockdep is enabled at the
moment asserting to avoid unnecessary confusion, using the following
condition, debug_locks && !this_cpu_read(lockdep_recursion).

However, lockdep_{off,on}() are also used for disabling and enabling
lockdep for a simular purpose.  Add !lockdep_recursing(current) that is
updated by lockdep_{off,on}() to the condition so that the assertions
are aware of !__lockdep_enabled if lockdep_off()'ed.

Signed-off-by: Byungchul Park <byungchul at sk.com>
---
 include/linux/lockdep.h  |  3 ++-
 kernel/locking/lockdep.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index ef03d8808c10..c83fe95199db 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -303,6 +303,7 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 	lockdep_assert_once(!current->lockdep_depth)
 
 #define lockdep_recursing(tsk)	((tsk)->lockdep_recursion)
+extern bool lockdep_recursing_current(void);
 
 #define lockdep_pin_lock(l)	lock_pin_lock(&(l)->dep_map)
 #define lockdep_repin_lock(l,c)	lock_repin_lock(&(l)->dep_map, (c))
@@ -630,7 +631,7 @@ DECLARE_PER_CPU(int, hardirqs_enabled);
 DECLARE_PER_CPU(int, hardirq_context);
 DECLARE_PER_CPU(unsigned int, lockdep_recursion);
 
-#define __lockdep_enabled	(debug_locks && !this_cpu_read(lockdep_recursion))
+#define __lockdep_enabled	(debug_locks && !this_cpu_read(lockdep_recursion) && !lockdep_recursing_current())
 
 #define lockdep_assert_irqs_enabled()					\
 do {									\
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 6c984a55d5ed..d2805ce250cb 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -6889,3 +6889,13 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 	warn_rcu_exit(rcu);
 }
 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
+
+/*
+ * For avoiding header dependency when using (struct task_struct *)current
+ * and lockdep_recursing() at the same time.
+ */
+noinstr bool lockdep_recursing_current(void)
+{
+	return lockdep_recursing(current);
+}
+EXPORT_SYMBOL_GPL(lockdep_recursing_current);
-- 
2.17.1