[v2] random: remove mostly unused async readiness notifier

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 5a0fbcf05e63..11abdc5004ec 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -84,8 +84,6 @@  static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
 /* Various types of waiters for crng_init->CRNG_READY transition. */
 static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
 static struct fasync_struct *fasync;
-static DEFINE_SPINLOCK(random_ready_chain_lock);
-static RAW_NOTIFIER_HEAD(random_ready_chain);
 
 /* Control how we warn userspace. */
 static struct ratelimit_state urandom_warning =
@@ -142,51 +140,6 @@  int wait_for_random_bytes(void)
 }
 EXPORT_SYMBOL(wait_for_random_bytes);
 
-/*
- * Add a callback function that will be invoked when the input
- * pool is initialised.
- *
- * returns: 0 if callback is successfully added
- *	    -EALREADY if pool is already initialised (callback not called)
- */
-int __cold register_random_ready_notifier(struct notifier_block *nb)
-{
-	unsigned long flags;
-	int ret = -EALREADY;
-
-	if (crng_ready())
-		return ret;
-
-	spin_lock_irqsave(&random_ready_chain_lock, flags);
-	if (!crng_ready())
-		ret = raw_notifier_chain_register(&random_ready_chain, nb);
-	spin_unlock_irqrestore(&random_ready_chain_lock, flags);
-	return ret;
-}
-
-/*
- * Delete a previously registered readiness callback function.
- */
-int __cold unregister_random_ready_notifier(struct notifier_block *nb)
-{
-	unsigned long flags;
-	int ret;
-
-	spin_lock_irqsave(&random_ready_chain_lock, flags);
-	ret = raw_notifier_chain_unregister(&random_ready_chain, nb);
-	spin_unlock_irqrestore(&random_ready_chain_lock, flags);
-	return ret;
-}
-
-static void __cold process_random_ready_list(void)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&random_ready_chain_lock, flags);
-	raw_notifier_call_chain(&random_ready_chain, 0, NULL);
-	spin_unlock_irqrestore(&random_ready_chain_lock, flags);
-}
-
 #define warn_unseeded_randomness() \
 	if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
 		printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
@@ -775,7 +728,6 @@  static void __cold _credit_init_bits(size_t bits)
 	if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
 		crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */
 		execute_in_process_context(crng_set_ready, &set_ready);
-		process_random_ready_list();
 		wake_up_interruptible(&crng_init_wait);
 		kill_fasync(&fasync, SIGIO, POLL_IN);
 		pr_notice("crng init done\n");
diff --git a/include/linux/random.h b/include/linux/random.h
index 6af130c6edb9..d2360b2825b6 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -78,8 +78,6 @@  int __init random_init(const char *command_line);
 bool rng_is_initialized(void);
 bool rng_has_arch_random(void);
 int wait_for_random_bytes(void);
-int register_random_ready_notifier(struct notifier_block *nb);
-int unregister_random_ready_notifier(struct notifier_block *nb);
 
 /* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
  * Returns the result of the call to wait_for_random_bytes. */
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 20e9887faaaa..fb77f7bfd126 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -750,60 +750,38 @@  static int __init debug_boot_weak_hash_enable(char *str)
 }
 early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
 
-static DEFINE_STATIC_KEY_TRUE(not_filled_random_ptr_key);
-static siphash_key_t ptr_key __read_mostly;
+static DEFINE_STATIC_KEY_FALSE(filled_random_ptr_key);
 
 static void enable_ptr_key_workfn(struct work_struct *work)
 {
-	get_random_bytes(&ptr_key, sizeof(ptr_key));
-	/* Needs to run from preemptible context */
-	static_branch_disable(&not_filled_random_ptr_key);
+	static_branch_enable(&filled_random_ptr_key);
 }
 
-static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
-
-static int fill_random_ptr_key(struct notifier_block *nb,
-			       unsigned long action, void *data)
-{
-	/* This may be in an interrupt handler. */
-	queue_work(system_unbound_wq, &enable_ptr_key_work);
-	return 0;
-}
-
-static struct notifier_block random_ready = {
-	.notifier_call = fill_random_ptr_key
-};
-
-static int __init initialize_ptr_random(void)
-{
-	int ret;
-
-	/* Don't bother waiting for RNG to be ready if RDRAND is mixed in already. */
-	if (rng_has_arch_random()) {
-		enable_ptr_key_workfn(&enable_ptr_key_work);
-		return 0;
-	}
-
-	ret = register_random_ready_notifier(&random_ready);
-	if (!ret) {
-		return 0;
-	} else if (ret == -EALREADY) {
-		/* This is in preemptible context */
-		enable_ptr_key_workfn(&enable_ptr_key_work);
-		return 0;
-	}
-
-	return ret;
-}
-early_initcall(initialize_ptr_random);
-
 /* Maps a pointer to a 32 bit unique identifier. */
 static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
 {
+	static siphash_key_t ptr_key __read_mostly;
 	unsigned long hashval;
 
-	if (static_branch_unlikely(&not_filled_random_ptr_key))
-		return -EAGAIN;
+	if (!static_branch_likely(&filled_random_ptr_key)) {
+		static bool filled = false;
+		static DEFINE_SPINLOCK(filling);
+		static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
+		unsigned long flags;
+
+		if (!system_unbound_wq ||
+		    (!rng_is_initialized() && !rng_has_arch_random()) ||
+		    !spin_trylock_irqsave(&filling, flags))
+			return -EAGAIN;
+
+		if (!filled) {
+			get_random_bytes(&ptr_key, sizeof(ptr_key));
+			queue_work(system_unbound_wq, &enable_ptr_key_work);
+			filled = true;
+		}
+		spin_unlock_irqrestore(&filling, flags);
+	}
+
 
 #ifdef CONFIG_64BIT
 	hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);