kern/184677

[krichy at tvnetwork.hu]

Seems that pjd did a change which eliminated the zfsdev_state_lock on Fri 
Aug 12 07:04:16 2011 +0000, which might introduced a new deadlock 
situation. Any comments on this?


Kojedzinszky Richard
Euronet Magyarorszag Informatikai Zrt.

On Mon, 16 Dec 2013, krichy at tvnetwork.hu wrote:

> Date: Mon, 16 Dec 2013 11:08:11 +0100 (CET)
> From: krichy at tvnetwork.hu
> To: freebsd-fs at freebsd.org
> Subject: kern/184677
> 
> Dear devs,
>
> I've attached a patch, which makes the recursive lockmgr disappear, and makes 
> the reported bug to disappear. I dont know if I followed any guidelines well, 
> or not, but at least it works for me. Please some ZFS/FreeBSD fs expert 
> review it, and fix it where it needed.
>
> But unfortunately, my original problem is still not solved, maybe the same as 
> Ryan's: 
> http://lists.freebsd.org/pipermail/freebsd-fs/2013-December/018707.html
>
> Tracing the problem down is that zfsctl_snapdir_lookup() tries to acquire 
> spa_namespace_lock while when finishing a zfs send -R does a zfsdev_close(), 
> and that also holds the same mutex. And this causes a deadlock scenario. I 
> looked at illumos's code, and for some reason they use another mutex on 
> zfsdev_close(), which therefore may not deadlock with 
> zfsctl_snapdir_lookup(). But I am still investigating the problem.
>
> I would like to help making ZFS more stable on freebsd also with its whole 
> functionality. I would be very thankful if some expert would give some 
> advice, how to solve these bugs. PJD, Steven, Xin?
>
> Thanks in advance,
>
>
> Kojedzinszky Richard
> Euronet Magyarorszag Informatikai Zrt.