3 files changed, 85 insertions, 17 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 13a7c6ae3fec..8de3b012eac7 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -26,7 +26,8 @@ obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
 	 gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
-	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o
+	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
+	 once.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += hexdump.o
diff --git a/lib/once.c b/lib/once.c
new file mode 100644
index 000000000000..05c8604627eb
--- /dev/null
+++ b/lib/once.c
@@ -0,0 +1,62 @@
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/once.h>
+#include <linux/random.h>
+
+struct once_work {
+	struct work_struct work;
+	struct static_key *key;
+};
+
+static void once_deferred(struct work_struct *w)
+{
+	struct once_work *work;
+
+	work = container_of(w, struct once_work, work);
+	BUG_ON(!static_key_enabled(work->key));
+	static_key_slow_dec(work->key);
+	kfree(work);
+}
+
+static void once_disable_jump(struct static_key *key)
+{
+	struct once_work *w;
+
+	w = kmalloc(sizeof(*w), GFP_ATOMIC);
+	if (!w)
+		return;
+
+	INIT_WORK(&w->work, once_deferred);
+	w->key = key;
+	schedule_work(&w->work);
+}
+
+static DEFINE_SPINLOCK(once_lock);
+
+bool __do_once_start(bool *done, unsigned long *flags)
+	__acquires(once_lock)
+{
+	spin_lock_irqsave(&once_lock, *flags);
+	if (*done) {
+		spin_unlock_irqrestore(&once_lock, *flags);
+		/* Keep sparse happy by restoring an even lock count on
+		 * this lock. In case we return here, we don't call into
+		 * __do_once_done but return early in the DO_ONCE() macro.
+		 */
+		__acquire(once_lock);
+		return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(__do_once_start);
+
+void __do_once_done(bool *done, struct static_key *once_key,
+		    unsigned long *flags)
+	__releases(once_lock)
+{
+	*done = true;
+	spin_unlock_irqrestore(&once_lock, *flags);
+	once_disable_jump(once_key);
+}
+EXPORT_SYMBOL(__do_once_done);
diff --git a/lib/random32.c b/lib/random32.c
index 0bee183fa18f..12111910ccd0 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -181,7 +181,7 @@ void prandom_seed(u32 entropy)
 	 * No locking on the CPUs, but then somewhat random results are, well,
 	 * expected.
 	 */
-	for_each_possible_cpu (i) {
+	for_each_possible_cpu(i) {
 		struct rnd_state *state = &per_cpu(net_rand_state, i);
 
 		state->s1 = __seed(state->s1 ^ entropy, 2U);
@@ -201,7 +201,7 @@ static int __init prandom_init(void)
 	prandom_state_selftest();
 
 	for_each_possible_cpu(i) {
-		struct rnd_state *state = &per_cpu(net_rand_state,i);
+		struct rnd_state *state = &per_cpu(net_rand_state, i);
 		u32 weak_seed = (i + jiffies) ^ random_get_entropy();
 
 		prandom_seed_early(state, weak_seed, true);
@@ -238,13 +238,30 @@ static void __init __prandom_start_seed_timer(void)
 	add_timer(&seed_timer);
 }
 
+void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
+{
+	int i;
+
+	for_each_possible_cpu(i) {
+		struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
+		u32 seeds[4];
+
+		get_random_bytes(&seeds, sizeof(seeds));
+		state->s1 = __seed(seeds[0],   2U);
+		state->s2 = __seed(seeds[1],   8U);
+		state->s3 = __seed(seeds[2],  16U);
+		state->s4 = __seed(seeds[3], 128U);
+
+		prandom_warmup(state);
+	}
+}
+
 /*
  *	Generate better values after random number generator
  *	is fully initialized.
  */
 static void __prandom_reseed(bool late)
 {
-	int i;
 	unsigned long flags;
 	static bool latch = false;
 	static DEFINE_SPINLOCK(lock);
@@ -266,19 +283,7 @@ static void __prandom_reseed(bool late)
 		goto out;
 
 	latch = true;
-
-	for_each_possible_cpu(i) {
-		struct rnd_state *state = &per_cpu(net_rand_state,i);
-		u32 seeds[4];
-
-		get_random_bytes(&seeds, sizeof(seeds));
-		state->s1 = __seed(seeds[0],   2U);
-		state->s2 = __seed(seeds[1],   8U);
-		state->s3 = __seed(seeds[2],  16U);
-		state->s4 = __seed(seeds[3], 128U);
-
-		prandom_warmup(state);
-	}
+	prandom_seed_full_state(&net_rand_state);
 out:
 	spin_unlock_irqrestore(&lock, flags);
 }