From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Wiele <jan@wiele.org>
Subject: Re: Hang in bcache/qemu
Date: Thu, 19 Jan 2017 15:06:15 +0100
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References: <2059985.veGUll5WnS@j-t460p> <4700072.elc5RSLsh5@j-t460p> <20170119134244.f6bydzrfsghq57ll@moria.home.lan>
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To: Kent Overstreet <kent.overstreet@gmail.com>
Cc: linux-bcache@vger.kernel.org

Am Donnerstag, 19. Januar 2017, 04:42:44 CET schrieb Kent Overstreet:
> On Thu, Jan 19, 2017 at 01:22:47PM +0100, Jan Wiele wrote:
> > Am Mittwoch, 18. Januar 2017, 09:48:30 CET schrieb Andre Noll:
> > > On Wed, Jan 18, 04:35, Kai Krakow wrote
> > > 
> > > FWIW, I'm seeing this as well on different hardware, and with both
> > > deadline and CFQ, so it's not a scheduler issue. The problem seems to
> > > be the bcache writeback thread calling down_write(&dc->writeback_lock)
> > > while already holding this lock.
> > 
> > Yes, the bug doesn't get triggered when the caching mechanism is set to
> > writethrough.
> 
> Is there something else blocked that's holding writeback_lock?

I'm not seeing any other blocked tasks in the kernel log, if it is that what 
you mean. 

If you could provide me with some instructions to follow on a hang, I will try 
to reproduce it next weekend.