Index: head/UPDATING
===================================================================
--- head/UPDATING
+++ head/UPDATING
@@ -31,6 +31,12 @@
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20190416:
+	The loadable random module KPI has changed; the random_infra_init()
+	routine now requires a 3rd function pointer for a bool (*)(void)
+	method that returns true if the random device is seeded (and
+	therefore unblocked).
+
 20190404:
 	r345895 reverts r320698. This implies that an nfsuserd(8) daemon
 	built from head sources between r320757 (July 6, 2017) and
Index: head/share/man/man9/Makefile
===================================================================
--- head/share/man/man9/Makefile
+++ head/share/man/man9/Makefile
@@ -1668,6 +1668,7 @@
 	psignal.9 tdsignal.9
 MLINKS+=random.9 arc4rand.9 \
 	random.9 arc4random.9 \
+	random.9 is_random_seeded.9 \
 	random.9 read_random.9 \
 	random.9 read_random_uio.9 \
 	random.9 srandom.9
Index: head/share/man/man9/random.9
===================================================================
--- head/share/man/man9/random.9
+++ head/share/man/man9/random.9
@@ -26,13 +26,14 @@
 .\"
 .\" $FreeBSD$
 .\" "
-.Dd April 15, 2019
+.Dd April 16, 2019
 .Dt RANDOM 9
 .Os
 .Sh NAME
 .Nm arc4rand ,
 .Nm arc4random ,
 .Nm arc4random_buf ,
+.Nm is_random_seeded ,
 .Nm random ,
 .Nm read_random ,
 .Nm read_random_uio ,
@@ -48,6 +49,8 @@
 .Fn arc4rand "void *ptr" "u_int length" "int reseed"
 .Pp
 .In sys/random.h
+.Ft bool
+.Fn is_random_seeded "void"
 .Ft void
 .Fn read_random "void *buffer" "int count"
 .Ft int
@@ -106,6 +109,13 @@
 instead, use the
 .Fn arc4rand
 family of functions.
+.Pp
+The
+.Fn is_random_seeded
+function can be used to check in advance if
+.Fn read_random
+will block.
+(If random is seeded, it will not block.)
 .Pp
 The
 .Fn read_random_uio
Index: head/sys/dev/random/random_infra.c
===================================================================
--- head/sys/dev/random/random_infra.c
+++ head/sys/dev/random/random_infra.c
@@ -63,12 +63,20 @@
 	panic("%s: no random module is loaded", __func__);
 }
 
+static bool
+null_is_random_seeded(void)
+{
+	return (false);
+}
+
 struct random_readers {
 	int	(*read_random_uio)(struct uio *, bool);
 	void	(*read_random)(void *, u_int);
+	bool	(*is_random_seeded)(void);
 } random_reader_context = {
 	(int (*)(struct uio *, bool))nullop,
 	null_read_random,
+	null_is_random_seeded,
 };
 
 struct sx randomdev_config_lock;
@@ -82,12 +90,15 @@
 SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_FIRST, random_infra_sysinit, NULL);
 
 void
-random_infra_init(int (*p_random_read_uio)(struct uio *, bool), void (*p_random_read)(void *, u_int))
+random_infra_init(int (*p_random_read_uio)(struct uio *, bool),
+    void (*p_random_read)(void *, u_int),
+    bool (*p_is_random_seeded)(void))
 {
 
 	RANDOM_CONFIG_X_LOCK();
 	random_reader_context.read_random_uio = p_random_read_uio;
 	random_reader_context.read_random = p_random_read;
+	random_reader_context.is_random_seeded = p_is_random_seeded;
 	RANDOM_CONFIG_X_UNLOCK();
 }
 
@@ -98,6 +109,7 @@
 	RANDOM_CONFIG_X_LOCK();
 	random_reader_context.read_random_uio = (int (*)(struct uio *, bool))nullop;
 	random_reader_context.read_random = null_read_random;
+	random_reader_context.is_random_seeded = null_is_random_seeded;
 	RANDOM_CONFIG_X_UNLOCK();
 }
 
@@ -128,5 +140,14 @@
 	random_reader_context.read_random(buf, len);
 	RANDOM_CONFIG_S_UNLOCK();
 }
+
+bool
+is_random_seeded(void)
+{
+	RANDOM_CONFIG_S_LOCK();
+	random_reader_context.is_random_seeded();
+	RANDOM_CONFIG_S_UNLOCK();
+}
+
 
 #endif /* defined(RANDOM_LOADABLE) */
Index: head/sys/dev/random/randomdev.h
===================================================================
--- head/sys/dev/random/randomdev.h
+++ head/sys/dev/random/randomdev.h
@@ -118,7 +118,8 @@
 #define	RANDOM_CONFIG_S_LOCK(x)		sx_slock(&randomdev_config_lock)
 #define	RANDOM_CONFIG_S_UNLOCK(x)	sx_sunlock(&randomdev_config_lock)
 #define	RANDOM_CONFIG_DEINIT_LOCK(x)	sx_destroy(&randomdev_config_lock)
-void random_infra_init(int (*)(struct uio *, bool), void (*)(void *, u_int));
+void random_infra_init(int (*)(struct uio *, bool), void (*)(void *, u_int),
+    bool (*)(void));
 void random_infra_uninit(void);
 #endif
 
Index: head/sys/dev/random/randomdev.c
===================================================================
--- head/sys/dev/random/randomdev.c
+++ head/sys/dev/random/randomdev.c
@@ -62,11 +62,14 @@
 #if defined(RANDOM_LOADABLE)
 #define READ_RANDOM_UIO	_read_random_uio
 #define READ_RANDOM	_read_random
+#define IS_RANDOM_SEEDED	_is_random_seeded
 static int READ_RANDOM_UIO(struct uio *, bool);
 static void READ_RANDOM(void *, u_int);
+static bool IS_RANDOM_SEEDED(void);
 #else
 #define READ_RANDOM_UIO	read_random_uio
 #define READ_RANDOM	read_random
+#define IS_RANDOM_SEEDED	is_random_seeded
 #endif
 
 static d_read_t randomdev_read;
@@ -93,7 +96,7 @@
 	p_random_alg_context = &random_alg_context;
 	p_random_alg_context->ra_init_alg(data);
 #if defined(RANDOM_LOADABLE)
-	random_infra_init(READ_RANDOM_UIO, READ_RANDOM);
+	random_infra_init(READ_RANDOM_UIO, READ_RANDOM, IS_RANDOM_SEEDED);
 #endif
 }
 
@@ -269,6 +272,12 @@
 
 		explicit_bzero(remainder_buf, sizeof(remainder_buf));
 	}
+}
+
+bool
+IS_RANDOM_SEEDED(void)
+{
+	return (p_random_alg_context->ra_seeded());
 }
 
 static __inline void
Index: head/sys/sys/param.h
===================================================================
--- head/sys/sys/param.h
+++ head/sys/sys/param.h
@@ -60,7 +60,7 @@
  *		in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1300018	/* Master, propagated to newvers */
+#define __FreeBSD_version 1300019	/* Master, propagated to newvers */
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,
Index: head/sys/sys/random.h
===================================================================
--- head/sys/sys/random.h
+++ head/sys/sys/random.h
@@ -40,6 +40,7 @@
 #if defined(DEV_RANDOM)
 void read_random(void *, u_int);
 int read_random_uio(struct uio *, bool);
+bool is_random_seeded(void);
 #else
 static __inline int
 read_random_uio(void *a __unused, u_int b __unused)
@@ -49,6 +50,11 @@
 static __inline void
 read_random(void *a __unused, u_int b __unused)
 {
+}
+static __inline bool
+is_random_seeded(void)
+{
+	return (false);
 }
 #endif