From c848ca572d4b1f4274e5f35076b92877520d7d0c Mon Sep 17 00:00:00 2001
From: Ksawlii <ksawery.blaszczak@proton.me>
Date: Sun, 24 Nov 2024 00:23:13 +0100
Subject: [PATCH] Revert "lockdep: fix deadlock issue between lockdep and rcu"

This reverts commit 6624949ecaf4370eca748067a48296e240e23553.
---
 kernel/locking/lockdep.c | 48 ++++++++++++++--------------------------
 1 file changed, 16 insertions(+), 32 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b576dd005..7471d85f5 100755
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5967,27 +5967,25 @@ static struct pending_free *get_pending_free(void)
 static void free_zapped_rcu(struct rcu_head *cb);
 
 /*
-* See if we need to queue an RCU callback, must called with
-* the lockdep lock held, returns false if either we don't have
-* any pending free or the callback is already scheduled.
-* Otherwise, a call_rcu() must follow this function call.
-*/
-static bool prepare_call_rcu_zapped(struct pending_free *pf)
+ * Schedule an RCU callback if no RCU callback is pending. Must be called with
+ * the graph lock held.
+ */
+static void call_rcu_zapped(struct pending_free *pf)
 {
 	WARN_ON_ONCE(inside_selftest());
 
 	if (list_empty(&pf->zapped))
-		return false;
+		return;
 
 	if (delayed_free.scheduled)
-		return false;
+		return;
 
 	delayed_free.scheduled = true;
 
 	WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
 	delayed_free.index ^= 1;
 
-	return true;
+	call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
 }
 
 /* The caller must hold the graph lock. May be called from RCU context. */
@@ -6013,7 +6011,6 @@ static void free_zapped_rcu(struct rcu_head *ch)
 {
 	struct pending_free *pf;
 	unsigned long flags;
-	bool need_callback;
 
 	if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
 		return;
@@ -6025,18 +6022,14 @@ static void free_zapped_rcu(struct rcu_head *ch)
 	pf = delayed_free.pf + (delayed_free.index ^ 1);
 	__free_zapped_classes(pf);
 	delayed_free.scheduled = false;
-	need_callback =
-		prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index);
-	lockdep_unlock();
-	raw_local_irq_restore(flags);
 
 	/*
-	* If there's pending free and its callback has not been scheduled,
-	* queue an RCU callback.
-	*/
-	if (need_callback)
-		call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
+	 * If there's anything on the open list, close and start a new callback.
+	 */
+	call_rcu_zapped(delayed_free.pf + delayed_free.index);
 
+	lockdep_unlock();
+	raw_local_irq_restore(flags);
 }
 
 /*
@@ -6076,7 +6069,6 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size)
 {
 	struct pending_free *pf;
 	unsigned long flags;
-	bool need_callback;
 
 	init_data_structures_once();
 
@@ -6084,11 +6076,10 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size)
 	lockdep_lock();
 	pf = get_pending_free();
 	__lockdep_free_key_range(pf, start, size);
-	need_callback = prepare_call_rcu_zapped(pf);
+	call_rcu_zapped(pf);
 	lockdep_unlock();
 	raw_local_irq_restore(flags);
-	if (need_callback)
-		call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
+
 	/*
 	 * Wait for any possible iterators from look_up_lock_class() to pass
 	 * before continuing to free the memory they refer to.
@@ -6182,7 +6173,6 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock)
 	struct pending_free *pf;
 	unsigned long flags;
 	int locked;
-	bool need_callback = false;
 
 	raw_local_irq_save(flags);
 	locked = graph_lock();
@@ -6191,13 +6181,11 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock)
 
 	pf = get_pending_free();
 	__lockdep_reset_lock(pf, lock);
-	need_callback = prepare_call_rcu_zapped(pf);
+	call_rcu_zapped(pf);
 
 	graph_unlock();
 out_irq:
 	raw_local_irq_restore(flags);
-	if (need_callback)
-		call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
 }
 
 /*
@@ -6241,7 +6229,6 @@ void lockdep_unregister_key(struct lock_class_key *key)
 	struct pending_free *pf;
 	unsigned long flags;
 	bool found = false;
-	bool need_callback = false;
 
 	might_sleep();
 
@@ -6262,14 +6249,11 @@ void lockdep_unregister_key(struct lock_class_key *key)
 	if (found) {
 		pf = get_pending_free();
 		__lockdep_free_key_range(pf, key, 1);
-		need_callback = prepare_call_rcu_zapped(pf);
+		call_rcu_zapped(pf);
 	}
 	lockdep_unlock();
 	raw_local_irq_restore(flags);
 
-	if (need_callback)
-		call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
-
 	/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
 	synchronize_rcu();
 }