diff --git a/share/man/man4/snd_uaudio.4 b/share/man/man4/snd_uaudio.4
--- a/share/man/man4/snd_uaudio.4
+++ b/share/man/man4/snd_uaudio.4
@@ -86,16 +86,6 @@
 by
 .An Hiten Pandya Aq Mt hmp@FreeBSD.org .
 .Sh BUGS
-The
-.Tn PCM
-framework in
-.Fx
-only supports synchronous device detach.
-That means all mixer and DSP character devices belonging to a given
-USB audio device must be closed when receiving an error on a DSP read,
-a DSP write or a DSP IOCTL request.
-Else the USB audio driver will wait for this to happen, preventing
-enumeration of new devices on the parenting USB controller.
 .Pp
 Some USB audio devices might refuse to work properly unless the sample
 rate is configured the same for both recording and playback, even if
diff --git a/sys/dev/sound/clone.h b/sys/dev/sound/clone.h
--- a/sys/dev/sound/clone.h
+++ b/sys/dev/sound/clone.h
@@ -102,6 +102,7 @@
 int snd_clone_enable(struct snd_clone *);
 int snd_clone_disable(struct snd_clone *);
 int snd_clone_getsize(struct snd_clone *);
+int snd_clone_getrefcount(struct snd_clone *);
 int snd_clone_getmaxunit(struct snd_clone *);
 int snd_clone_setmaxunit(struct snd_clone *, int);
 int snd_clone_getdeadline(struct snd_clone *);
@@ -112,6 +113,8 @@
 uint32_t snd_clone_setdevflags(struct cdev *, uint32_t);
 int snd_clone_gc(struct snd_clone *);
 void snd_clone_destroy(struct snd_clone *);
+void snd_clone_sleep(struct snd_clone *, struct mtx *);
+void snd_clone_wakeup(struct snd_clone *);
 int snd_clone_acquire(struct cdev *);
 int snd_clone_release(struct cdev *);
 int snd_clone_ref(struct cdev *);
diff --git a/sys/dev/sound/clone.c b/sys/dev/sound/clone.c
--- a/sys/dev/sound/clone.c
+++ b/sys/dev/sound/clone.c
@@ -37,10 +37,7 @@
 #include "opt_snd.h"
 #endif
 
-#if defined(SND_DIAGNOSTIC) || defined(SND_DEBUG)
 #include <dev/sound/pcm/sound.h>
-#endif
-
 #include <dev/sound/clone.h>
 
 /*
@@ -80,6 +77,7 @@
 struct snd_clone {
 	TAILQ_HEAD(link_head, snd_clone_entry) head;
 	struct timespec tsp;
+	struct cv cv;
 	int refcount;
 	int size;
 	int typemask;
@@ -115,6 +113,7 @@
 	    ("invalid clone flags=0x%08x", flags));
 
 	c = malloc(sizeof(*c), M_DEVBUF, M_WAITOK | M_ZERO);
+	cv_init(&c->cv, "clone");
 	c->refcount = 0;
 	c->size = 0;
 	c->typemask = typemask;
@@ -188,6 +187,14 @@
 	return (c->size);
 }
 
+int
+snd_clone_getrefcount(struct snd_clone *c)
+{
+	SND_CLONE_ASSERT(c != NULL, ("NULL snd_clone"));
+
+	return (c->refcount);
+}
+
 int
 snd_clone_getmaxunit(struct snd_clone *c)
 {
@@ -342,7 +349,7 @@
 				ce->pid = -1;
 			} else {
 				TAILQ_REMOVE(&c->head, ce, link);
-				destroy_dev(ce->devt);
+				destroy_dev_sched(ce->devt);
 				free(ce, M_DEVBUF);
 				c->size--;
 			}
@@ -370,9 +377,26 @@
 		ce = tmp;
 	}
 
+	cv_destroy(&c->cv);
 	free(c, M_DEVBUF);
 }
 
+void
+snd_clone_sleep(struct snd_clone *c, struct mtx *lock)
+{
+	SND_CLONE_ASSERT(c != NULL, ("NULL snd_clone"));
+
+	cv_wait(&c->cv, lock);
+}
+
+void
+snd_clone_wakeup(struct snd_clone *c)
+{
+	SND_CLONE_ASSERT(c != NULL, ("NULL snd_clone"));
+
+	cv_broadcastpri(&c->cv, PRIBIO);
+}
+
 /*
  * snd_clone_acquire() : The vital part of concurrency management. Must be
  * called somewhere at the beginning of open() handler. ENODEV is not really
@@ -489,6 +513,9 @@
 	    (c->refcount == 0 && (c->flags & SND_CLONE_GC_LASTREF))))
 		(void)snd_clone_gc(c);
 
+	if (c->refcount == 0)
+		snd_clone_wakeup(ce->parent);
+
 	return (c->refcount);
 }
 
diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c
--- a/sys/dev/sound/pcm/dsp.c
+++ b/sys/dev/sound/pcm/dsp.c
@@ -796,14 +796,7 @@
 	 * cleanup process.
 	 */
 	(void)snd_clone_release(i_dev);
-
-	/*
-	 * destroy_dev() might sleep, so release pcm lock
-	 * here and rely on pcm cv serialization.
-	 */
-	PCM_UNLOCK(d);
 	(void)snd_clone_unref(i_dev);
-	PCM_LOCK(d);
 
 	PCM_RELEASE(d);
 	PCM_UNLOCK(d);
diff --git a/sys/dev/sound/pcm/sound.h b/sys/dev/sound/pcm/sound.h
--- a/sys/dev/sound/pcm/sound.h
+++ b/sys/dev/sound/pcm/sound.h
@@ -399,6 +399,7 @@
 #define	PCM_MODE_PLAY		0x02
 #define	PCM_MODE_REC		0x04
 
+#define PCM_LOCKPTR(d)		((d)->lock)
 #define PCM_LOCKOWNED(d)	mtx_owned((d)->lock)
 #define	PCM_LOCK(d)		mtx_lock((d)->lock)
 #define	PCM_UNLOCK(d)		mtx_unlock((d)->lock)
diff --git a/sys/dev/sound/pcm/sound.c b/sys/dev/sound/pcm/sound.c
--- a/sys/dev/sound/pcm/sound.c
+++ b/sys/dev/sound/pcm/sound.c
@@ -1176,39 +1176,40 @@
 
 	CHN_FOREACH(ch, d, channels.pcm) {
 		CHN_LOCK(ch);
-		if (ch->refcount > 0) {
-			device_printf(dev,
-			    "unregister: channel %s busy (pid %d)\n",
-			    ch->name, ch->pid);
-			CHN_UNLOCK(ch);
-			PCM_RELEASE_QUICK(d);
-			return (EBUSY);
+		if (ch->flags & CHN_F_SLEEPING) {
+			/*
+			 * We are detaching, so do not wait for the timeout in
+			 * chn_read()/chn_write(). Wake up the thread and kill
+			 * the channel immediately.
+			 */
+			CHN_BROADCAST(&ch->intr_cv);
+			ch->flags |= CHN_F_DEAD;
 		}
 		CHN_UNLOCK(ch);
 	}
 
 	if (d->clones != NULL) {
-		if (snd_clone_busy(d->clones) != 0) {
-			device_printf(dev, "unregister: clone busy\n");
+		while (snd_clone_getrefcount(d->clones) > 0) {
 			PCM_RELEASE_QUICK(d);
-			return (EBUSY);
-		} else {
+			/*
+			 * Wait for all sleeping threads to drain so that we
+			 * can destroy the clones safely.
+			 */
 			PCM_LOCK(d);
-			(void)snd_clone_disable(d->clones);
+			snd_clone_sleep(d->clones, PCM_LOCKPTR(d));
 			PCM_UNLOCK(d);
+			PCM_ACQUIRE_QUICK(d);
 		}
-	}
-
-	if (mixer_uninit(dev) == EBUSY) {
-		device_printf(dev, "unregister: mixer busy\n");
 		PCM_LOCK(d);
-		if (d->clones != NULL)
-			(void)snd_clone_enable(d->clones);
-		PCM_RELEASE(d);
+		(void)snd_clone_disable(d->clones);
 		PCM_UNLOCK(d);
-		return (EBUSY);
 	}
 
+	/*
+	 * TODO explain
+	 */
+	(void)mixer_uninit(dev);
+
 	/* remove /dev/sndstat entry first */
 	sndstat_unregister(dev);
 
diff --git a/sys/dev/sound/usb/uaudio.c b/sys/dev/sound/usb/uaudio.c
--- a/sys/dev/sound/usb/uaudio.c
+++ b/sys/dev/sound/usb/uaudio.c
@@ -1250,20 +1250,12 @@
 	unsigned i = uaudio_get_child_index_by_dev(sc, dev);
 	int error = 0;
 
-repeat:
-	if (sc->sc_child[i].pcm_registered) {
+	if (sc->sc_child[i].pcm_registered)
 		error = pcm_unregister(dev);
-	} else {
-		if (sc->sc_child[i].mixer_init)
-			error = mixer_uninit(dev);
-	}
+	else if (sc->sc_child[i].mixer_init)
+		error = mixer_uninit(dev);
 
-	if (error) {
-		device_printf(dev, "Waiting for sound application to exit!\n");
-		usb_pause_mtx(NULL, 2 * hz);
-		goto repeat;		/* try again */
-	}
-	return (0);			/* success */
+	return (error);
 }
 
 static int