[PATCH v4 06/15] locking/lockdep: Make it easy to detect whether or not inside a selftest

[Bart Van Assche <bvanassche@acm.org>]

The patch that frees unused lock classes will modify the behavior of
lockdep_free_key_range() and lockdep_reset_lock() depending on whether
or not these functions are called from the context of the lockdep
selftests. Hence make it easy to detect whether or not lockdep code
is called from the context of a lockdep selftest.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 include/linux/lockdep.h  | 2 ++
 kernel/locking/lockdep.c | 1 +
 lib/locking-selftest.c   | 2 ++
 3 files changed, 5 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b5e6bfe0ae4a..16ac9fe56783 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -466,6 +466,8 @@ enum xhlock_context_t {
 #define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
 	{ .name = (_name), .key = (void *)(_key), }
 
+extern struct task_struct *lockdep_selftest_task_struct;
+
 static inline void lockdep_invariant_state(bool force) {}
 static inline void lockdep_init_task(struct task_struct *task) {}
 static inline void lockdep_free_task(struct task_struct *task) {}
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 4fcc2a07bfb4..aeb775a4bed3 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -81,6 +81,7 @@ module_param(lock_stat, int, 0644);
  * code to recurse back into the lockdep code...
  */
 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+struct task_struct *lockdep_selftest_task_struct;
 
 static int graph_lock(void)
 {
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 1e1bbf171eca..b37fd3fe7fd6 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -1989,6 +1989,7 @@ void locking_selftest(void)
 
 	init_shared_classes();
 	debug_locks_silent = !debug_locks_verbose;
+	lockdep_selftest_task_struct = current;
 
 	DO_TESTCASE_6R("A-A deadlock", AA);
 	DO_TESTCASE_6R("A-B-B-A deadlock", ABBA);
@@ -2097,5 +2098,6 @@ void locking_selftest(void)
 		printk("---------------------------------\n");
 		debug_locks = 1;
 	}
+	lockdep_selftest_task_struct = NULL;
 	debug_locks_silent = 0;
 }
-- 
2.20.0.rc2.403.gdbc3b29805-goog