One thread per port, not per device.
796 ? S 0:00 \_ [scsi_eh_0]
797 ? S 0:00 \_ [scsi_eh_1]
798 ? S 0:00 \_ [scsi_eh_2]
819 ? S 0:00 \_ [scsi_eh_3]
820 ? S 0:00 \_ [scsi_eh_4]
824 ? S 0:00 \_ [scsi_eh_5]
825 ? S 0:14 \_ [scsi_eh_6]
bardioc ~ # lsscsi -d
[0:0:0:0] disk ATA ST3160827AS 3.42 /dev/sda[8:0]
[1:0:0:0] disk ATA ST3160827AS 3.42 /dev/sdb[8:16]
[5:0:0:0] disk ATA IBM-DHEA-36480 HE8O /dev/sdc[8:32]
[5:0:1:0] disk ATA Maxtor 6L160P0 BAH4 /dev/sdd[8:48]
[6:0:0:0] cd/dvd HL-DT-ST DVDRAM GSA-4081B A100 /dev/sr0[11:0]
bardioc ~ # lsscsi -H
[0] sata_promise
[1] sata_promise
[2] sata_promise
[3] sata_via
[4] sata_via
[5] pata_via
[6] pata_via
The bad is, that there is always a thread, even if the hardware is not
even hotplug capable.
Don't know if the thread is even needed for hotplug...