Comment 2 for bug 1302437

StacktraceTop:
 __GI___pthread_mutex_lock (mutex=0x0) at ../nptl/pthread_mutex_lock.c:66
 libusb_get_device_list (ctx=0x0, list=list@entry=0x7fffffb6cca8) at ../../libusb/core.c:671
 musb_probe_devices (lst=lst@entry=0x7fffffb6d1f0 "", lst_size=lst_size@entry=16384, cnt=cnt@entry=0x7fffffb6d13c) at io/hpmud/musb.c:2037
 hpmud_probe_devices (bus=bus@entry=HPMUD_BUS_ALL, buf=buf@entry=0x7fffffb6d1f0 "", buf_size=buf_size@entry=16384, cnt=cnt@entry=0x7fffffb6d13c, bytes_read=bytes_read@entry=0x7fffffb6d140) at io/hpmud/hpmud.c:598
 device_discovery () at prnt/backend/hp.c:493