Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace

[Steven Rostedt]

On Sat, 21 Mar 2009, Ingo Molnar wrote:

> 
> * Ingo Molnar <mingo@xxxxxxx> wrote:
> 
> > 
> > * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > 
> > > 
> > > On Fri, 20 Mar 2009, Frederic Weisbecker wrote:
> > > > > >  
> > > > > >  	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
> > > > > > -	set_user_nice(current, 19);
> > > > > > +	set_user_nice(current, -1);
> > > > > >  	if (irqreader && cur_ops->irqcapable)
> > > > > >  		setup_timer_on_stack(&t, rcu_torture_timer, 0);
> > > > > 
> > > > > i dont have a reproducer right now. Can you trigger it with latest 
> > > > > -tip, which has this commit included:
> > > > > 
> > > > > 04cb9ac: rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to o
> > > > > 
> > > > > ?
> > > > > 
> > > > > 	Ingo
> > > > 
> > > > 
> > > > I tested three times the same things but with 04cb9ac and... it didn't triggered
> > > > anymore :-)
> > > 
> > > So lets hope that was the culprit.
> > > 
> > > Great work Frederic!
> > 
> > No new lockups of this nature in overnight -tip testing. It's 
> > still a bit too early to tell for sure but it's promising ;-)
> 
> just got a lockup again :-/ It hangs here:
> 
> calling  init_mmio_trace+0x0/0x12 @ 1
> initcall init_mmio_trace+0x0/0x12 returned 0 after 0 usecs
> calling  init_graph_trace+0x0/0x12 @ 1
> Testing tracer function_graph: 
> 
> and this time i got good stackdumps as well - see below. Config 
> attached.

> CONFIG_CLASSIC_RCU=y

All the crashes you reported only happen with classic RCU.

Paul,

Did anything change recently that could cause this lockup?

-- Steve
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