Re: [Bug 18632] "INFO: task" dpkg "blocked for more than 120 seconds.

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Jun 09, 2011 at 06:02:41AM +0800, Andrew Morton wrote:
> (udate by email because bugzilla is broken)
> 
> On Wed, 8 Jun 2011 21:38:43 GMT
> bugzilla-daemon@bugzilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=18632
> 
> I always get a bit worried when I see dm-crypt involved - it doesn't
> seem terribly well-behaved or reliable.
> 
> That being said, some of the other reports here indicate that we are
> hitting a sync() livelock, sometimes fsync().

These comments all mention "blocked sync(1) on concurrent heavy writes".

        Comment #6 From Douglas Augusto
        Comment #12 From Nathan Grennan 
        Comment #16 From justincase@yopmail.com 
        Comment #23 From Carlos Alberto Lopez Perez

Comment #17 From Justin Wheeler is special in that fio is doing
read-only IO. Is it updating the mtime and the mtime writes are in
turn starved by the higher-priority continuous reads? (or at least the
write speed cannot keep up with the new mtime dirties)

> A pile of patches from
> Wu Fengguang which could/should address these issues is about to hit
> the linux-next tree.

Some livelock fixes will show up in tomorrow's linux-next tree. As for
now the fixes are available here:

git://git.kernel.org/pub/scm/linux/kernel/git/wfg/writeback.git fs-writeback

Thanks,
Fengguang