Re: Blocked tasks on 3.15.1

[Duncan <1i5t5.duncan@cox.net>]

Tomasz Chmielewski posted on Fri, 27 Jun 2014 12:02:43 +0200 as excerpted:

>> I've been getting blocked tasks on 3.15.1 generally at times when the
>> filesystem is somewhat busy (such as doing a backup via scp/clonezilla
>> writing to the disk).
> 
> I've started seeing similar on several servers, after upgrading to 3.15
> or 3.15.1. With 3.16-rc1 it was even crashing for me.
> I've rolled back to the latest 3.14.x, and it's still behaving fine.
> 
> I've signalled it before on the list in "btrfs filesystem hang with
> 3.15-rc3 when doing rsync" thread.

There is a known btrfs lockup bug that was introduced in the commit-
window btrfs pull for 3.16, that was fixed by a pull I believe the day 
before 3.16-rc2.  So 3.16-pre to rc2 is known-bad tho it'll work for a 
few minutes and didn't do any permanent damage that I could see, here.

But from 3.16-rc2 on, the 3.16-pre series has been working fine for me.

For 3.15, I didn't run the pre-releases as I had another project I was 
focusing on, but I experienced no problems with 3.15 itself.  However, my 
use-case is multiple independent small btrfs on partitioned SSD, sub-100-
GB per btrfs, so I'd be less likely to experience the blocked task issues 
that others reported, mostly on TB+ size spinning rust.

And it /did/ seem to me that the frequency of blocked-task reports were 
higher for 3.15 than for previous kernel series, tho 3.15 worked fine for 
me on small btrfs on SSD, the relatively short time I ran it.

Hopefully that problem's fixed on 3.16-rc2+, but as of yet there's not 
enough 3.16-rc2+ reports out there from folks experiencing issues with 
3.15 blocked tasks to rightfully say.  What CAN be said is that the known 
3.16-series commit-window btrfs lockups bug that DID affect me was fixed 
right before rc2, and I'm running rc2+ just fine, here.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman