On Fri, 2017-06-30 at 17:28 +1000, Nicholas Piggin wrote:

On Fri, 30 Jun 2017 10:52:18 +0530
Abdul Haleem [off-list ref] wrote:

quoted

On Fri, 2017-06-30 at 00:45 +1000, Nicholas Piggin wrote:

quoted

On Thu, 29 Jun 2017 20:23:05 +1000
Nicholas Piggin [off-list ref] wrote:

quoted

On Thu, 29 Jun 2017 19:36:14 +1000
Nicholas Piggin [off-list ref] wrote:

quoted

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I don't *think* the replay-wakeup-interrupt patch is directly involved, but
it's likely to be one of the idle patches.  

Okay this turned out to be misconfigured sleep states I added for the
simulator, sorry for the false alarm.

quoted

Although you have this in the backtrace. I wonder if that's a stuck
lock in rcu_process_callbacks?

So this spinlock becomes top of the list of suspects. Can you try
enabling lockdep and try to reproduce it?

Yes, recreated again with CONFIG_LOCKDEP=y & CONFIG_DEBUG_LOCKDEP=y set.
I do not see any difference in trace messages with and without LOCKDEP
enabled.

Please find the attached log file.

Can you get an rcu_invoke_callback event trace that Paul suggested?

Yes, I was able to collect the perf data for rcu_invoke_callback event
on recent next kernel (4.12.0-next-20170705). the issue is rare to hit.

After booting the next kernel, I started this command 'perf record  -e
rcu:rcu_invoke_callback -a -g -- cat' and waited for 30 minutes.

five minutes after seeing the stalls messages, I did CTRL-C to end the
perf command.

@Nicholas : the perf.data report is too huge to attach here, shall I
ping you the internal location of file on slack/mail ? Also the machine
is in the same state if you want to use it ?

Does this bug show up with just the powerpc next branch?

Thanks,
Nick

-- 
Regard's

Abdul Haleem
IBM Linux Technology Centre