diff --git a/sys/kern/kern_intr.c b/sys/kern/kern_intr.c
--- a/sys/kern/kern_intr.c
+++ b/sys/kern/kern_intr.c
@@ -636,7 +636,15 @@
 			free(ih, M_ITHREAD);
 			return (EINVAL);
 		}
+		/* We can't mix sleepable and non-sleepable handlers and events */
+		if (((flags & INTR_SLEEPABLE) == 0) != ((ie->ie_flags & IE_SLEEPABLE) == 0)) {
+			mtx_unlock(&ie->ie_lock);
+			free(ih, M_ITHREAD);
+			return (EINVAL);
+		}
 	}
+	if (flags & INTR_SLEEPABLE)
+		ie->ie_flags |= IE_SLEEPABLE;
 
 	/* Create a thread if we need one. */
 	while (ie->ie_thread == NULL && handler != NULL) {
@@ -1191,10 +1199,10 @@
 {
 
 	/* Interrupt handlers should not sleep. */
-	if (!(ie->ie_flags & IE_SOFT))
+	if (!(ie->ie_flags & (IE_SOFT | IE_SLEEPABLE)))
 		THREAD_NO_SLEEPING();
 	intr_event_execute_handlers(p, ie);
-	if (!(ie->ie_flags & IE_SOFT))
+	if (!(ie->ie_flags & (IE_SOFT | IE_SLEEPABLE)))
 		THREAD_SLEEPING_OK();
 
 	/*
diff --git a/sys/sys/bus.h b/sys/sys/bus.h
--- a/sys/sys/bus.h
+++ b/sys/sys/bus.h
@@ -280,7 +280,8 @@
 	INTR_MD1 = 4096,		/* flag reserved for MD use */
 	INTR_MD2 = 8192,		/* flag reserved for MD use */
 	INTR_MD3 = 16384,		/* flag reserved for MD use */
-	INTR_MD4 = 32768		/* flag reserved for MD use */
+	INTR_MD4 = 32768,		/* flag reserved for MD use */
+	INTR_SLEEPABLE = 65536
 };
 
 enum intr_trigger {
diff --git a/sys/sys/interrupt.h b/sys/sys/interrupt.h
--- a/sys/sys/interrupt.h
+++ b/sys/sys/interrupt.h
@@ -129,6 +129,7 @@
 
 /* Interrupt event flags kept in ie_flags. */
 #define	IE_SOFT		0x000001	/* Software interrupt. */
+#define	IE_SLEEPABLE	0x000002	/* Sleepable ithread */
 #define	IE_ADDING_THREAD 0x000004	/* Currently building an ithread. */
 
 /* Flags to pass to swi_sched. */