linux-kernel - [PATCH v5 06/15] locking/lockdep: Make it easy to detect whether or not inside a selftest

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Message-Id: <20181217213002.73776-7-bvanassche@acm.org>
Date:   Mon, 17 Dec 2018 13:29:53 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, tj@...nel.org, longman@...hat.com,
        johannes.berg@...el.com, linux-kernel@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        Johannes Berg <johannes@...solutions.net>
Subject: [PATCH v5 06/15] 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.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Johannes Berg <johannes@...solutions.net>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 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 4fcc2a07bfb4..aa04aa9a46cb 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;
 }
-- 
2.20.0.405.gbc1bbc6f85-goog