Index: sys/dev/random/random_harvestq.c
===================================================================
--- sys/dev/random/random_harvestq.c
+++ sys/dev/random/random_harvestq.c
@@ -34,7 +34,9 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/ck.h>
 #include <sys/conf.h>
+#include <sys/epoch.h>
 #include <sys/eventhandler.h>
 #include <sys/hash.h>
 #include <sys/kernel.h>
@@ -80,6 +82,14 @@
 
 static u_int read_rate;
 
+/*
+ * Random must initialize much earlier than epoch, but we can initialize the
+ * epoch code before SMP starts.  Prior to SMP, we can safely bypass
+ * concurrency primitives.
+ */
+static __read_mostly bool epoch_inited;
+static __read_mostly epoch_t rs_epoch;
+
 /*
  * How many events to queue up. We create this many items in
  * an 'empty' queue, then transfer them to the 'harvest' queue with
@@ -99,12 +109,12 @@
 __read_frequently u_int hc_source_mask;
 
 struct random_sources {
-	LIST_ENTRY(random_sources)	 rrs_entries;
+	CK_LIST_ENTRY(random_sources)	 rrs_entries;
 	struct random_source		*rrs_source;
 };
 
-static LIST_HEAD(sources_head, random_sources) source_list =
-    LIST_HEAD_INITIALIZER(source_list);
+static CK_LIST_HEAD(sources_head, random_sources) source_list =
+    CK_LIST_HEAD_INITIALIZER(source_list);
 
 SYSCTL_NODE(_kern_random, OID_AUTO, harvest, CTLFLAG_RW, 0,
     "Entropy Device Parameters");
@@ -230,6 +240,14 @@
 SYSINIT(random_device_h_proc, SI_SUB_KICK_SCHEDULER, SI_ORDER_ANY, kproc_start,
     &random_proc_kp);
 
+static void
+rs_epoch_init(void *dummy __unused)
+{
+	rs_epoch = epoch_alloc("Random Sources", 0);
+	epoch_inited = true;
+}
+SYSINIT(rs_epoch_init, SI_SUB_TASKQ + 1, SI_ORDER_ANY, rs_epoch_init, NULL);
+
 /*
  * Run through all fast sources reading entropy for the given
  * number of rounds, which should be a multiple of the number
@@ -241,6 +259,9 @@
 	uint32_t entropy[HARVESTSIZE];
 	struct random_sources *rrs;
 	u_int i, n, local_read_rate;
+	bool rse_warm;
+
+	rse_warm = epoch_inited;
 
 	/*
 	 * Step over all of live entropy sources, and feed their output
@@ -256,7 +277,9 @@
 	local_read_rate = MAX(local_read_rate, 1);
 	/* But not exceeding RANDOM_KEYSIZE_WORDS */
 	local_read_rate = MIN(local_read_rate, RANDOM_KEYSIZE_WORDS);
-	LIST_FOREACH(rrs, &source_list, rrs_entries) {
+	if (rse_warm)
+		epoch_enter(rs_epoch);
+	CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
 		for (i = 0; i < p_random_alg_context->ra_poolcount*local_read_rate; i++) {
 			n = rrs->rrs_source->rs_read(entropy, sizeof(entropy));
 			KASSERT((n <= sizeof(entropy)), ("%s: rs_read returned too much data (%u > %zu)", __func__, n, sizeof(entropy)));
@@ -276,6 +299,8 @@
 			random_harvest_direct(entropy, n, rrs->rrs_source->rs_source);
 		}
 	}
+	if (rse_warm)
+		epoch_exit(rs_epoch);
 	explicit_bzero(entropy, sizeof(entropy));
 #if defined(RANDOM_LOADABLE)
 	}
@@ -614,7 +639,10 @@
 	random_harvest_register_source(rsource->rs_source);
 
 	printf("random: registering fast source %s\n", rsource->rs_ident);
-	LIST_INSERT_HEAD(&source_list, rrs, rrs_entries);
+
+	RANDOM_HARVEST_LOCK();
+	CK_LIST_INSERT_HEAD(&source_list, rrs, rrs_entries);
+	RANDOM_HARVEST_UNLOCK();
 }
 
 void
@@ -626,13 +654,17 @@
 
 	random_harvest_deregister_source(rsource->rs_source);
 
-	LIST_FOREACH(rrs, &source_list, rrs_entries)
+	RANDOM_HARVEST_LOCK();
+	CK_LIST_FOREACH(rrs, &source_list, rrs_entries)
 		if (rrs->rrs_source == rsource) {
-			LIST_REMOVE(rrs, rrs_entries);
+			CK_LIST_REMOVE(rrs, rrs_entries);
 			break;
 		}
-	if (rrs != NULL)
-		free(rrs, M_ENTROPY);
+	RANDOM_HARVEST_UNLOCK();
+
+	if (rrs != NULL && epoch_inited)
+		epoch_wait(rs_epoch);
+	free(rrs, M_ENTROPY);
 }
 
 static int
@@ -642,13 +674,19 @@
 	struct sbuf sbuf;
 	int error, count;
 
+	error = sysctl_wire_old_buffer(req, 0);
+	if (error != 0)
+		return (error);
+
 	sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
 	count = 0;
-	LIST_FOREACH(rrs, &source_list, rrs_entries) {
+	epoch_enter(rs_epoch);
+	CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
 		sbuf_cat(&sbuf, (count++ ? ",'" : "'"));
 		sbuf_cat(&sbuf, rrs->rrs_source->rs_ident);
 		sbuf_cat(&sbuf, "'");
 	}
+	epoch_exit(rs_epoch);
 	error = sbuf_finish(&sbuf);
 	sbuf_delete(&sbuf);
 	return (error);