linux-kernel - Re: [PATCH tip/core/rcu 1/2] rcu: Parallelize and economize NOCB kthread wakeups

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Date:	Fri, 22 Aug 2014 17:54:53 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, riel@...hat.com, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, dvhart@...ux.intel.com, fweisbec@...il.com,
	oleg@...hat.com, sbw@....edu
Subject: Re: [PATCH tip/core/rcu 1/2] rcu: Parallelize and economize NOCB
 kthread wakeups

On (Mon) 18 Aug 2014 [21:01:49], Paul E. McKenney wrote:

> The odds are low over the next few days.  I am adding nastier rcutorture
> testing, however.  It would still be very good to get debug information
> from your setup.  One approach would be to convert the trace function
> calls into printk(), if that would help.

I added a few printks on the lines of the traces in cases where
rcu_nocb_poll was checked -- since that reproduces the hang.  Are the
following traces sufficient, or should I keep adding more printks?

In the case of rcu-trace-nopoll.txt, the messages stop after a while
(when the guest locks up hard).  That's when I kill the qemu process.


		Amit

View attachment "rcu-trace-nopoll.txt" of type "text/plain" (158712 bytes)

View attachment "rcu-traces-poll.txt" of type "text/plain" (36084 bytes)