kern/92164: SCSI target mode LOR

[Attila Nagy]

>Number:         92164
>Category:       kern
>Synopsis:       SCSI target mode LOR
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jan 22 17:50:03 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Attila Nagy
>Release:        7-CURRENT
>Organization:
-
>Environment:
7-CURRENT as of today.
>Description:
I'm doing some experiments with FreeBSD target mode support on Fibre Channel and thought that I should give CURRENT a try too.

The machine itself is an HP BL25p with 8 GB of RAM (but hw.physmem set to under 4G, it seems the isp driver needs this) and dual Opterons. Running amd64 code.

This is what I get after issuing
scsi_target -A -S -T -W 32 2:0:0 /data/file1

lock order reversal: (sleepable after non-sleepable)
 1st 0xffffffff808ce680 targ global (targ global) @ /usr/src/sys/cam/scsi/scsi_target.c:418
 2nd 0xffffffff808e98c0 kernel environment (kernel environment) @ /usr/src/sys/kern/subr_hints.c:117
KDB: stack backtrace:
witness_checkorder() at witness_checkorder+0x4f9
_sx_slock() at _sx_slock+0x4d
res_find() at res_find+0x41a
resource_find() at resource_find+0x7e
resource_find_dev() at resource_find_dev+0x5f
cam_periph_alloc() at cam_periph_alloc+0x1df
targioctl() at targioctl+0x3a7
giant_ioctl() at giant_ioctl+0x65
devfs_ioctl_f() at devfs_ioctl_f+0x6f
ioctl() at ioctl+0x147
syscall() at syscall+0x517
Xfast_syscall() at Xfast_syscall+0xa8
--- syscall (54, FreeBSD ELF64, ioctl), rip = 0x800909aac, rsp = 0x7fffffffbb98, rbp = 0x7fffffffe700 ---

>How-To-Repeat:

>Fix:
6-STABLE works, at least the above command can be used without a LOR or panic.
But there are some other concerns with target mode, which could be improved.
>Release-Note:
>Audit-Trail:
>Unformatted: