From: "Paul E. McKenney" <redacted>
Date: Tue, 25 Jul 2017 20:55:45 -0700

On Tue, Jul 25, 2017 at 02:10:29PM -0700, David Miller wrote:

quoted

Just to report, turning softlockup back on fixes things for me on
sparc64 too.

Very good!

quoted

The thing about softlockup is it runs an hrtimer, which seems to run
about every 4 seconds.

I could see where that could shake things loose, but I am surprised that
it would be needed.  I ran a short run with CONFIG_SOFTLOCKUP_DETECTOR=y
with no trouble, but I will be running a longer test later on.

quoted

So I wonder if this is a NO_HZ problem.

Might be.  My tests run with NO_HZ_FULL=n and NO_HZ_IDLE=y.  What are
you running?  (Again, my symptoms are slightly different, so I might
be seeing a different bug.)

I run with NO_HZ_FULL=n and NO_HZ_IDLE=y, just like you.

To clarify, the symptoms show up with SOFTLOCKUP_DETECTOR disabled.