Merge branch 'bpf_random32'

Daniel Borkmann says:

====================
BPF/random32 updates

BPF update to split the prandom state apart, and to move the
*once helpers to the core. For details, please see individual
patches. Given the changes and since it's in the tree for
quite some time, net-next is a better choice in our opinion.

v1 -> v2:
 - Make DO_ONCE() type-safe, remove the kvec helper. Credits
   go to Alexei Starovoitov for the __VA_ARGS__ hint, thanks!
 - Add a comment to the DO_ONCE() helper as suggested by Alexei.
 - Rework prandom_init_once() helper to the new API.
 - Keep Alexei's Acked-by on the last patch.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 62 insertions, 0 deletions

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);