devclass: make devclass_alloc_unit use M_NOWAIT

The only caller already does this.

The routine can be called with a mutex held making M_WAITOK illegal.

Sponsored by:	Rubicon Communications, LLC ("Netgate")

Author: mjguzik

sys/kern/subr_bus.c

@@ -1208,6 +1208,7 @@ devclass_get_sysctl_tree(devclass_t dc)
 static int
 devclass_alloc_unit(devclass_t dc, device_t dev, int *unitp)
 {
+	device_t *devices;
 	const char *s;
 	int unit = *unitp;
 
@@ -1264,8 +1265,11 @@ devclass_alloc_unit(devclass_t dc, device_t dev, int *unitp)
 		int newsize;
 
 		newsize = unit + 1;
-		dc->devices = reallocf(dc->devices,
-		    newsize * sizeof(*dc->devices), M_BUS, M_WAITOK);
+		devices = reallocf(dc->devices,
+		    newsize * sizeof(*dc->devices), M_BUS, M_NOWAIT);
+		if (devices == NULL)
+			return (ENOMEM);
+		dc->devices = devices;
 		memset(dc->devices + dc->maxunit, 0,
 		    sizeof(device_t) * (newsize - dc->maxunit));
 		dc->maxunit = newsize;