[tip:locking/core] locking/lockdep: Make it easy to detect whether or not inside a selftest

[tip-bot for Bart Van Assche]

Commit-ID:  cdc84d794947b5431c0a6916c303aee7114819d2
Gitweb:     https://git.kernel.org/tip/cdc84d794947b5431c0a6916c303aee7114819d2
Author:     Bart Van Assche <bvanassche@xxxxxxx>
AuthorDate: Thu, 14 Feb 2019 15:00:44 -0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 28 Feb 2019 07:55:43 +0100

locking/lockdep: Make it easy to detect whether or not inside a selftest

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.

Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: johannes.berg@xxxxxxxxx
Cc: tj@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20190214230058.196511-10-bvanassche@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/lockdep.h  | 5 +++++
 kernel/locking/lockdep.c | 6 ++++++
 lib/locking-selftest.c   | 2 ++
 3 files changed, 13 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b5e6bfe0ae4a..66eee1ba0f2a 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -265,6 +265,7 @@ extern void lockdep_reset(void);
 extern void lockdep_reset_lock(struct lockdep_map *lock);
 extern void lockdep_free_key_range(void *start, unsigned long size);
 extern asmlinkage void lockdep_sys_exit(void);
+extern void lockdep_set_selftest_task(struct task_struct *task);
 
 extern void lockdep_off(void);
 extern void lockdep_on(void);
@@ -395,6 +396,10 @@ static inline void lockdep_on(void)
 {
 }
 
+static inline void lockdep_set_selftest_task(struct task_struct *task)
+{
+}
+
 # define lock_acquire(l, s, t, r, c, n, i)	do { } while (0)
 # define lock_release(l, n, i)			do { } while (0)
 # define lock_downgrade(l, i)			do { } while (0)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2d4c21a02546..34cd87c65f5d 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;
+static struct task_struct *lockdep_selftest_task_struct;
 
 static int graph_lock(void)
 {
@@ -331,6 +332,11 @@ void lockdep_on(void)
 }
 EXPORT_SYMBOL(lockdep_on);
 
+void lockdep_set_selftest_task(struct task_struct *task)
+{
+	lockdep_selftest_task_struct = task;
+}
+
 /*
  * Debugging switches:
  */
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 1e1bbf171eca..a1705545e6ac 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_set_selftest_task(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_set_selftest_task(NULL);
 	debug_locks_silent = 0;
 }