diff --git a/sys/dev/sound/pcm/channel.c b/sys/dev/sound/pcm/channel.c
--- a/sys/dev/sound/pcm/channel.c
+++ b/sys/dev/sound/pcm/channel.c
@@ -128,6 +128,7 @@
 	struct pcm_channel *c;
 	int i;
 
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
@@ -146,6 +147,7 @@
 		PCM_RELEASE(d);
 		PCM_UNLOCK(d);
 	}
+	bus_topo_unlock();
 }
 
 static int
@@ -166,7 +168,7 @@
 	return (0);
 }
 SYSCTL_PROC(_hw_snd, OID_AUTO, vpc_0db,
-    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NEEDGIANT, 0, sizeof(int),
+    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
     sysctl_hw_snd_vpc_0db, "I",
     "0db relative level");
 
@@ -186,7 +188,7 @@
 	return (0);
 }
 SYSCTL_PROC(_hw_snd, OID_AUTO, vpc_reset,
-    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 0, sizeof(int),
+    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, sizeof(int),
     sysctl_hw_snd_vpc_reset, "I",
     "reset volume on all channels");
 
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
@@ -2068,6 +2068,7 @@
 	if (ai->dev == -1 && i_dev->si_devsw != &dsp_cdevsw)
 		return (EINVAL);
 
+	bus_topo_lock();
 	for (unit = 0; pcm_devclass != NULL &&
 	    unit < devclass_get_maxunit(pcm_devclass); unit++) {
 		d = devclass_get_softc(pcm_devclass, unit);
@@ -2075,6 +2076,7 @@
 			if ((ai->dev == -1 && unit == snd_unit) ||
 			    ai->dev == unit) {
 				dsp_oss_audioinfo_unavail(ai, unit);
+				bus_topo_unlock();
 				return (0);
 			} else {
 				d = NULL;
@@ -2093,6 +2095,7 @@
 			d = NULL;
 		}
 	}
+	bus_topo_unlock();
 
 	/* Exhausted the search -- nothing is locked, so return. */
 	if (d == NULL)
@@ -2252,6 +2255,7 @@
 	 * Search for the requested audio device (channel).  Start by
 	 * iterating over pcm devices.
 	 */ 
+	bus_topo_lock();
 	for (unit = 0; pcm_devclass != NULL &&
 	    unit < devclass_get_maxunit(pcm_devclass); unit++) {
 		d = devclass_get_softc(pcm_devclass, unit);
@@ -2406,9 +2410,12 @@
 
 		PCM_UNLOCK(d);
 
-		if (devname != NULL)
+		if (devname != NULL) {
+			bus_topo_unlock();
 			return (0);
+		}
 	}
+	bus_topo_unlock();
 
 	/* Exhausted the search -- nothing is locked, so return. */
 	return (EINVAL);
diff --git a/sys/dev/sound/pcm/feeder_rate.c b/sys/dev/sound/pcm/feeder_rate.c
--- a/sys/dev/sound/pcm/feeder_rate.c
+++ b/sys/dev/sound/pcm/feeder_rate.c
@@ -258,6 +258,7 @@
 	 * set resampler quality if and only if it is exist as
 	 * part of feeder chains and the channel is idle.
 	 */
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
@@ -280,10 +281,12 @@
 		PCM_UNLOCK(d);
 	}
 
+	bus_topo_unlock();
+
 	return (0);
 }
 SYSCTL_PROC(_hw_snd, OID_AUTO, feeder_rate_quality,
-    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NEEDGIANT, 0, sizeof(int),
+    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
     sysctl_hw_snd_feeder_rate_quality, "I",
     "sample rate converter quality ("__XSTRING(Z_QUALITY_MIN)"=low .. "
     __XSTRING(Z_QUALITY_MAX)"=high)");
diff --git a/sys/dev/sound/pcm/mixer.c b/sys/dev/sound/pcm/mixer.c
--- a/sys/dev/sound/pcm/mixer.c
+++ b/sys/dev/sound/pcm/mixer.c
@@ -1444,12 +1444,14 @@
 	 * There's a 1:1 relationship between mixers and PCM devices, so
 	 * begin by iterating over PCM devices and search for our mixer.
 	 */
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
 		if (!PCM_REGISTERED(d) || PCM_DETACHING(d)) {
 			if ((mi->dev == -1 && i == snd_unit) || mi->dev == i) {
 				mixer_oss_mixerinfo_unavail(mi, i);
+				bus_topo_unlock();
 				return (0);
 			} else
 				continue;
@@ -1470,6 +1472,7 @@
 		if (d->mixer_dev->si_drv1 == NULL) {
 			mixer_oss_mixerinfo_unavail(mi, i);
 			PCM_UNLOCK(d);
+			bus_topo_unlock();
 			return (0);
 		}
 
@@ -1550,8 +1553,10 @@
 
 		PCM_UNLOCK(d);
 
+		bus_topo_unlock();
 		return (0);
 	}
+	bus_topo_unlock();
 
 	return (EINVAL);
 }
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
@@ -188,7 +188,7 @@
 }
 /* XXX: do we need a way to let the user change the default unit? */
 SYSCTL_PROC(_hw_snd, OID_AUTO, default_unit,
-    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_ANYBODY | CTLFLAG_NEEDGIANT, 0,
+    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_ANYBODY | CTLFLAG_MPSAFE, 0,
     sizeof(int), sysctl_hw_snd_default_unit, "I",
     "default sound device");
 
@@ -337,6 +337,7 @@
 
 	best = -1;
 	bestprio = -100;
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
@@ -352,6 +353,8 @@
 			bestprio = prio;
 		}
 	}
+	bus_topo_unlock();
+
 	return (best);
 }
 
@@ -713,6 +716,7 @@
 
 	j = 0;
 
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
@@ -739,6 +743,7 @@
 
 		PCM_UNLOCK(d);
 	}
+	bus_topo_unlock();
 
 	si->numsynths = 0;	/* OSSv4 docs:  this field is obsolete */
 	/**
@@ -759,9 +764,11 @@
 	 * break if they try to loop through all mixers and some of them are
 	 * not available.
 	 */
+	bus_topo_lock();
 	si->nummixers = devclass_get_maxunit(pcm_devclass);
 	si->numcards = devclass_get_maxunit(pcm_devclass);
 	si->numaudios = devclass_get_maxunit(pcm_devclass);
+	bus_topo_unlock();
 		/* OSSv4 docs:	Intended only for test apps; API doesn't
 		   really have much of a concept of cards.  Shouldn't be
 		   used by applications. */
@@ -787,6 +794,7 @@
 	struct snddev_info *d;
 	int i;
 
+	bus_topo_lock();
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
@@ -814,8 +822,11 @@
 			PCM_UNLOCK(d);
 		}
 
+		bus_topo_unlock();
 		return (0);
 	}
+	bus_topo_unlock();
+
 	return (ENXIO);
 }
 
diff --git a/sys/dev/sound/pcm/vchan.c b/sys/dev/sound/pcm/vchan.c
--- a/sys/dev/sound/pcm/vchan.c
+++ b/sys/dev/sound/pcm/vchan.c
@@ -1065,6 +1065,7 @@
 		if (v > SND_MAXVCHANS)
 			v = SND_MAXVCHANS;
 		snd_maxautovchans = v;
+		bus_topo_lock();
 		for (i = 0; pcm_devclass != NULL &&
 		    i < devclass_get_maxunit(pcm_devclass); i++) {
 			d = devclass_get_softc(pcm_devclass, i);
@@ -1074,11 +1075,12 @@
 			vchan_setmaxauto(d, v);
 			PCM_RELEASE_QUICK(d);
 		}
+		bus_topo_unlock();
 	}
 	return (error);
 }
 SYSCTL_PROC(_hw_snd, OID_AUTO, maxautovchans,
-    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NEEDGIANT, 0, sizeof(int),
+    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, sizeof(int),
     sysctl_hw_snd_maxautovchans, "I", "maximum virtual channel");
 
 void