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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Ingo Molnar <mingo@elte.hu>
Subject: Re: Help needed: Resume problems in 2.6.32-rc, perhaps related to preempt_count leakage in keventd
Date: Mon, 9 Nov 2009 13:24:37 +0100
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On Monday 09 November 2009, Ingo Molnar wrote:
> 
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> 
> > [ 2016.865041] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/29920                                                                                         
> > [ 2016.865344] caller is vmstat_update+0x13/0x48                                          
> > [ 2016.865522] Pid: 29920, comm: events/1 Not tainted 2.6.31-tst #158                     
> > [ 2016.865700] Call Trace:                                                                
> > [ 2016.865877]  [<ffffffff811608e8>] debug_smp_processor_id+0xc4/0xd4                     
> > [ 2016.866052]  [<ffffffff810a9ae1>] vmstat_update+0x13/0x48                              
> > [ 2016.866232]  [<ffffffff81051ee6>] worker_thread+0x18b/0x22a                            
> > [ 2016.866409]  [<ffffffff810a9ace>] ? vmstat_update+0x0/0x48                             
> > [ 2016.866578]  [<ffffffff810556a5>] ? autoremove_wake_function+0x0/0x38                  
> > [ 2016.866749]  [<ffffffff81288803>] ? _spin_unlock_irqrestore+0x35/0x37                  
> > [ 2016.866935]  [<ffffffff81051d5b>] ? worker_thread+0x0/0x22a                            
> > [ 2016.867113]  [<ffffffff8105547d>] kthread+0x69/0x71                                    
> > [ 2016.867278]  [<ffffffff8100c1aa>] child_rip+0xa/0x20                                   
> > [ 2016.867450]  [<ffffffff81055414>] ? kthread+0x0/0x71                                   
> > [ 2016.867618]  [<ffffffff8100c1a0>] ? child_rip+0x0/0x20                                 
> 
> a bug producing similar looking messages was fixed by:
> 
>   fd21073: sched: Fix affinity logic in select_task_rq_fair()
> 
> but that bug was introduced by:
> 
>   a1f84a3: sched: Check for an idle shared cache in select_task_rq_fair()

I guess these are tip commits?

> Which is for v2.6.33, not v2.6.32.

The one I saw was in the Linus' tree, quite obviously.

Also, I should have noted that the problem is not really easy to trigger.
Usually, it involves 20-25 suspend-resume cycles to reproduce it.  For this
reason the kernels that I mark as "good" may still be affected, although in
such a way that the problem is much harder to reproduce with them.

Thanks,
Rafael
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