scsi_target witness lock error

[Sean Bruno]

Nate Lawson wrote:
> Sean Bruno wrote:
>   
>> Alrighty, a little cleaner patch to allow sbp_targ.c to acutally work
>> under RELENG_6. http://www.consultcsg.com/RELENG_6.diff
>>
>> Also and update with the witness error.  And the kernel config I am using:
>> http://www.consultcsg.com/scsitarget_witness.txt
>> http://www.consultcsg.com/FIREWIRE_TGT
>>
>> Is scsi_target the only application that is making this kern env witness
>> error appear?  I find it hard to believe that nothing else in the code
>> base hits this type of problem?
>>     
>
> Apparently scsi_target wasn't fully tested when the CAM locking went in.
>  It was written before there was a design for CAM locking so it may need
> some reworking.  For example, it assumes that it should acquire/drop
> locks multiple times in its start method if there are multiple CCBs
> queued.  That may not be the fastest way, depending on contention for
> the SIM lock.
>
>   
Hmmm...I just applied(ripped off!) a RELENG_7 modifed version of 
kern_environment.c that uses non-sleepable mutex's and the witness went 
away.
http://www.consultcsg.com/kern_env.diff

It appears that you are on to something Nate with regard to the CAM 
locking.  scsi_target appears to be blocking on a call to cam_periph_lock():
http://www.consultcsg.com/cam_periph_lock.txt

Hidetoshi suggested a patch that I will now apply and retest:
http://consultcsg.com/scsi_target.c.diff

I do however, get a kernel panic when trying to exit from scsi_target 
via ctrl-c
http://www.consultcsg.com/knlist_lock.txt

Sean

P.S.  Is the URL based logging working better than a cut/paste into the 
email for everyone?