On Sat, 2014-02-01 at 05:21 +0100, Mike Galbraith wrote: 

On Fri, 2014-01-31 at 23:07 +0100, Sebastian Andrzej Siewior wrote: 

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* Mike Galbraith | 2014-01-17 06:17:12 [+0100]:

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On Thu, 2014-01-16 at 23:22 -0500, Steven Rostedt wrote: 

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On Thu, 16 Jan 2014 04:08:57 +0100
Mike Galbraith [off-list ref] wrote:

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On Wed, 2014-01-15 at 20:58 -0500, Steven Rostedt wrote:

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3.2.53-rt76-rc1 stable review patch.
If anyone has any objections, please let me know.

Not sure this is needed without the tglx don't unconditionally raise
timer softirq patch, and with that patch applied in the form it exists
in 3.12-rt9, as well as this one, you'll still eventually deadlock.

Hmm, I'll have to take a look. This sounds to be missing from all the
stable -rt kernels. I'll be pulling in the latest updates from 3.12-rt
soon.

Below are the two deadlocks I encountered with 3.12-rt9, which has both
$subject and timers-do-not-raise-softirq-unconditionally.patch applied.

This patch was introduced because we had a deadlock in
run_local_timers() which took a sleeping lock in hardirq context. This
seem not to be the case in v3.2 therefore I would suggest not to take
this patch here because it does not fix anything.

Mike, do you see these deadlocks with 3.12.*-rt11 as well?

No.  I beat 64 core box hard configured both nohz_idle and nohz_full,
the only thing that fell out was the nohz_full irqs enabled warning.

Oh, and the softirq pending warnings appearing under heavy load.  I
hadn't gotten to chasing those, but I see they should be history.

I'll wedge the pending -rt11 fixes in, and let 64 core stress a bit
while you're kneading -rt12 dough.

-Mike