Reassigned to Paul.

Is this a regression?  Sounds like it.

Hello, Rolf!  Could you please post the offending .config and console log?  If the log is a silent hang, could you please force stack traces from sysrq or whatever you have handy?

Created attachment 28001 [details]
Config of 2.6.34.1

Used that config for 2.6.35 with "make oldconfig".

Thank you for the info, Rolf!

Could you please set CONFIG_RCU_CPU_STALL_DETECTOR=y and try again?  This diagnostic config option might print valuable information to the console.

(Of course, the console log from your previous hang would be very useful -- just knowing roughly where in the boot process the hang occurred would help me.)

Sorry, I had no time to try this yesterday. I'll be on vacation for the next 2 weeks.

Before I ran into this the issue was already known in #gentoo-hppa on Freenode IRC. Maybe you could ask for some tests there, the guys there also have affected machines at hand.

Thank you, Rolf -- I pointed that IRC channel to this bug.

On Monday, August 30, 2010, Rolf Eike Beer wrote:
> Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a report
> > of regressions introduced between 2.6.34 and 2.6.35.
> > 
> > The following bug entry is on the current list of known regressions
> > introduced between 2.6.34 and 2.6.35.  Please verify if it still should
> > be listed and let the tracking team know (either way).
> > 
> > 
> > Bug-Entry   : http://bugzilla.kernel.org/show_bug.cgi?id=16537
> > Subject             : TREE_RCU hangs at boot
> > Submitter   : Rolf Eike Beer <eike-kernel@sf-tec.de>
> > Date                : 2010-08-07 12:18 (23 days old)
> 
> Yes, this is a regression that is still unfixed.

Handled-By : Paul E. McKenney <paulmck@linux.vnet.ibm.com>

On Tuesday, September 21, 2010, Paul E. McKenney wrote:
> On Mon, Sep 20, 2010 at 11:26:27AM -0700, Paul E. McKenney wrote:
> > On Sun, Sep 12, 2010 at 09:08:42PM +0200, Rafael J. Wysocki wrote:
> > > This message has been generated automatically as a part of a report
> > > of regressions introduced between 2.6.34 and 2.6.35.
> > > 
> > > The following bug entry is on the current list of known regressions
> > > introduced between 2.6.34 and 2.6.35.  Please verify if it still should
> > > be listed and let the tracking team know (either way).
> > > 
> > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=16537
> > > Subject           : TREE_RCU hangs at boot
> > > Submitter : Rolf Eike Beer <eike-kernel@sf-tec.de>
> > > Date              : 2010-08-07 12:18 (37 days old)
> > > Handled-By        : Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > 
> > I cannot reproduce this.  The function that is claimed to hang contains
> > only printk()s.  I have asked the guys who can actually reproduce it
> > to try a later kernel, and will let you know how this goes.
> > 
> > If you cannot trust printk(), who can you trust?  ;-)
> 
> It turns out that this problem is due to tab processing in the PA-RISC
> firmware, which certainly explains my inability to reproduce it.  It
> turns out that it is fixed by:
> 
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d9b68e5e88248bb24fd4e455588bea1d56108fd6
> 
> So we can close this regression.
> 
> Many thanks to Guy Martin <gmsoft@tuxicoman.be> for much help with
> this!!!