linux-kernel - Re: [linux-next] cpus stalls detected few hours after booting next kernel

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Message-Id: <20170630181511.GC2393@linux.vnet.ibm.com>
Date:   Fri, 30 Jun 2017 11:15:11 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Abdul Haleem <abdhalee@...ux.vnet.ibm.com>,
        sachinp <sachinp@...ux.vnet.ibm.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Paul McKenney <Paul.McKenney@...ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-next <linux-next@...r.kernel.org>, paulus@...ba.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [linux-next] cpus stalls detected few hours after booting next
 kernel

On Fri, Jun 30, 2017 at 05:28:02PM +1000, Nicholas Piggin wrote:
> On Fri, 30 Jun 2017 10:52:18 +0530
> Abdul Haleem <abdhalee@...ux.vnet.ibm.com> wrote:
> 
> > On Fri, 2017-06-30 at 00:45 +1000, Nicholas Piggin wrote:
> > > On Thu, 29 Jun 2017 20:23:05 +1000
> > > Nicholas Piggin <npiggin@...il.com> wrote:
> > > 
> > > > On Thu, 29 Jun 2017 19:36:14 +1000
> > > > Nicholas Piggin <npiggin@...il.com> wrote:
> > > 
> > > > > 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.
> > > 
> > > > 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?
> 
> Does this bug show up with just the powerpc next branch?

And I must say that those RCU CPU stall warnings are spectacular!

Did you by chance boot with a small subset of the CPUs online, and
bring the rest online later on?

							Thanx, Paul