linux-kernel - [PATCH v3 7/8] locking/lockdep: Add lockdep_early

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Message-Id: <20200115214313.13253-8-longman@redhat.com>
Date:   Wed, 15 Jan 2020 16:43:12 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v3 7/8] locking/lockdep: Add lockdep_early_init() before any lock is taken

The lockdep_init() function is actually called after __lock_acquire()
has been called. So it is not a good place to do chain buckets
initialization. Fortunately, the check for nr_free_chain_hlocks prevents
those chain buckets from being used prematurely.

Add a lockdep_early_init() function that will be called very early in the
boot process and move chain buckets initialization over there to ensure
that the buckets are initialized before __lock_acquire() is called.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/lockdep.h  | 2 ++
 init/main.c              | 1 +
 kernel/locking/lockdep.c | 5 ++++-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c50d01ef1414..efb1ec28a2cd 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -279,6 +279,7 @@ struct held_lock {
  * Initialization, self-test and debugging-output methods:
  */
 extern void lockdep_init(void);
+extern void lockdep_early_init(void);
 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);
@@ -432,6 +433,7 @@ static inline void lockdep_set_selftest_task(struct task_struct *task)
 # define lock_set_class(l, n, k, s, i)		do { } while (0)
 # define lock_set_subclass(l, s, i)		do { } while (0)
 # define lockdep_init()				do { } while (0)
+# define lockdep_early_init()			do { } while (0)
 # define lockdep_init_map(lock, name, key, sub) \
 		do { (void)(name); (void)(key); } while (0)
 # define lockdep_set_class(lock, key)		do { (void)(key); } while (0)
diff --git a/init/main.c b/init/main.c
index 2cd736059416..571b83981276 100644
--- a/init/main.c
+++ b/init/main.c
@@ -580,6 +580,7 @@ asmlinkage __visible void __init start_kernel(void)
 	set_task_stack_end_magic(&init_task);
 	smp_setup_processor_id();
 	debug_objects_early_init();
+	lockdep_early_init();
 
 	cgroup_init_early();
 
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a1d839e522a9..165e2361b25e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5382,10 +5382,13 @@ void lockdep_unregister_key(struct lock_class_key *key)
 }
 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
 
-void __init lockdep_init(void)
+void __init lockdep_early_init(void)
 {
 	init_chain_block_buckets();
+}
 
+void __init lockdep_init(void)
+{
 	printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
 
 	printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
-- 
2.18.1