On Fri, 24 Jul 2015 21:02:26 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

On Wed, 22 Jul 2015, Steven Rostedt wrote:

quoted

It's still there. Note, that when I pull -rt into stable, I do a
 git quiltimport, which renames the patch set. It's now called:

 0089-slub-delay-ctor-until-the-object-is-requested.patch

quoted

From the 4.0.8-rt6 announce:

- The delayed kmem_cache constructor caused problems. Steven Rostedt
  reported problems versus the signal handling code and Koehrer
  Mathias reported the same. The patch in question has been reverted
  and a patch currently sitting in -mm has been added which provides
  the same functionality (running the constructor with enabled
  interrupts). Patch provided by Thomas Gleixner. 

The stable trees which carry the delay-ctor patches should be updated
to this.

Reverting the patch at least prevents the BUG. Latencywise the slub patch

   mm-slub-move-slab-initialization-into-irq-enabled-re.patch

is the one which wants to be ported back.

OK, I hope I did this right. Please go and test the latest 3.18-rc to
see if things work better.

To build 3.18.18-rt16-rc1 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.18.tar.xz

  http://www.kernel.org/pub/linux/kernel/v3.x/patch-3.18.18.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/3.18/patch-3.18.18-rt16-rc1.patch.xz

You can also build from 3.18.18-rt15 by applying the incremental patch:

http://www.kernel.org/pub/linux/kernel/projects/rt/3.18/incr/patch-3.18.18-rt15-rt16-rc1.patch.xz


-- Steve