% uname -m -v FreeBSD 10.1-STABLE #2 r274721M: Wed Dec 10 22:45:35 PST 2014 root@hairball:/usr/obj/usr/src/sys/GPZ-274721 amd64 Something seems to be wrong in the bookkeeping of "sa" devices, although it might not be specific to sa. Scsi tape changer is attached via "ahc0: <Adaptec 2940 Ultra2 SCSI adapter>" When I perform this sequence: - power on scsi tape changer - camcontrol rescan all - power off tape changer - camcontrol rescan all my system gets into a state where 1) /dev/sa2 does not exist; 2) /dev/sa2.[123] exist; and 3) further attempts to power on the tape changer + "camcontrol rescan all" yield the following in /var/log/messages: Dec 30 21:29:34 hairball kernel: cam_periph_alloc: attempt to re-allocate valid device sa2 rejected flags 0x198 refcount 0 Dec 30 21:29:34 hairball kernel: saasync: Unable to probe new device due to status 0x6 Dec 30 21:29:34 hairball kernel: ch0 at ahc0 bus 0 scbus5 target 3 lun 0 Dec 30 21:29:34 hairball kernel: ch0: <DELL PV-122T K17r> Removable Changer SCSI-2 device Dec 30 21:29:34 hairball kernel: ch0: Serial Number 0000000000 Dec 30 21:29:34 hairball kernel: ch0: 3.300MB/s transfers Dec 30 21:29:34 hairball kernel: ch0: 8 slots, 1 drive, 1 picker, 0 portals Dec 30 21:29:34 hairball kernel: ch0: quirks=0x2<NO_DVCID> I can pretty reliably get the system into this state. For what its worth, the appearance of this problem sometime between late 2013 and mid-2014 in 9-STABLE vs. 10-STABLE seemed to coincide with another occasional problem: power-on tape changer, and then system would lock up hard (with the motherboard beeper on solid) while executing either "camcontrol rescan all" or "camcontrol devlist". I have not been able to reproduce that behavior at will, but it's happened several times across several 10-STABLE versions I tried since July 2014.
As of 10-Stable r280974, this problem seems to be fixed (probably due to the sa(4) changes committed in the meantime).