Index: head/sys/kern/kern_malloc.c
===================================================================
--- head/sys/kern/kern_malloc.c
+++ head/sys/kern/kern_malloc.c
@@ -520,6 +520,10 @@
 	if (flags & M_WAITOK) {
 		KASSERT(curthread->td_intr_nesting_level == 0,
 		   ("malloc(M_WAITOK) in interrupt context"));
+#ifdef EPOCH_TRACE
+		if (__predict_false(curthread->td_epochnest > 0))
+			epoch_trace_list(curthread);
+#endif
 		KASSERT(curthread->td_epochnest == 0,
 			("malloc(M_WAITOK) in epoch context"));		
 	}
Index: head/sys/kern/kern_synch.c
===================================================================
--- head/sys/kern/kern_synch.c
+++ head/sys/kern/kern_synch.c
@@ -148,6 +148,10 @@
 	    ("sleeping without a lock"));
 	KASSERT(ident != NULL, ("_sleep: NULL ident"));
 	KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
+#ifdef EPOCH_TRACE
+	if (__predict_false(curthread->td_epochnest > 0))
+		epoch_trace_list(curthread);
+#endif
 	KASSERT(td->td_epochnest == 0, ("sleeping in an epoch section"));
 	if (priority & PDROP)
 		KASSERT(lock != NULL && lock != &Giant.lock_object,
Index: head/sys/kern/subr_epoch.c
===================================================================
--- head/sys/kern/subr_epoch.c
+++ head/sys/kern/subr_epoch.c
@@ -234,6 +234,17 @@
 	} else
 		SLIST_REMOVE_HEAD(&td->td_epochs, et_tlink);
 }
+
+/* Used by assertions that check thread state before going to sleep. */
+void
+epoch_trace_list(struct thread *td)
+{
+	epoch_tracker_t iet;
+
+	SLIST_FOREACH(iet, &td->td_epochs, et_tlink)
+		printf("Epoch %s entered at %s:%d\n", iet->et_epoch->e_name,
+		    iet->et_file, iet->et_line);
+}
 #endif /* EPOCH_TRACE */
 
 static void
Index: head/sys/kern/subr_trap.c
===================================================================
--- head/sys/kern/subr_trap.c
+++ head/sys/kern/subr_trap.c
@@ -166,6 +166,10 @@
 	WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
 	KASSERT(td->td_critnest == 0,
 	    ("userret: Returning in a critical section"));
+#ifdef EPOCH_TRACE
+	if (__predict_false(curthread->td_epochnest > 0))
+		epoch_trace_list(curthread);
+#endif
 	KASSERT(td->td_epochnest == 0,
 	    ("userret: Returning in an epoch section"));
 	KASSERT(td->td_locks == 0,
Index: head/sys/sys/epoch.h
===================================================================
--- head/sys/sys/epoch.h
+++ head/sys/sys/epoch.h
@@ -83,6 +83,7 @@
 void _epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE);
 void _epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE);
 #ifdef EPOCH_TRACE
+void epoch_trace_list(struct thread *);
 #define	epoch_enter_preempt(epoch, et)	_epoch_enter_preempt(epoch, et, __FILE__, __LINE__)
 #define	epoch_exit_preempt(epoch, et)	_epoch_exit_preempt(epoch, et, __FILE__, __LINE__)
 #else