On Tue, Apr 01, 2014 at 06:16:16PM -0400, Dave Jones wrote:
> On Tue, Apr 01, 2014 at 11:32:45AM -0700, Paul E. McKenney wrote:
>
> > > > Given that you have CONFIG_RCU_TRACE=y, could you please enable the
> > > > following trace events and dump the trace before things hang?
> > > >
> > > > trace_event=rcu:rcu_grace_period,rcu:rcu_grace_period_init
> > > >
> > > > If it is not feasible to dump the trace before things hang, let me
> > > > know, and I will work out some other diagnostic regime.
> > >
> > > I'll give that a shot when I get back in a few hours.
>
> ok, this is tricky, and I'm not sure how helpful the below is.
> because I don't know when the hang is going to happen, in parallel to my
> usual workload
> I did this..
> while [ 1 ];
> do
> cat trace
> echo > trace
> done
>
> and got this...
>
>
>
> # entries-in-buffer/entries-written: 7/7 #P:4
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / delay
> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> # | | | |||| | |
> <idle>-0 [000] dNs3 851.748475: rcu_grace_period: rcu_preempt
> 21342 cpuend
> <idle>-0 [000] dNs3 851.748477: rcu_grace_period: rcu_preempt
> 21343 cpustart
> <idle>-0 [000] dNs3 851.748477: rcu_grace_period: rcu_sched
> 20080 cpuend
> <idle>-0 [000] dN.2 851.748480: rcu_grace_period: rcu_preempt
> 21343 cpuqs
> rcu_preempt-9 [000] ...1 851.748485: rcu_grace_period: rcu_preempt
> 21343 fqsstart
> rcu_preempt-9 [000] ...1 851.748487: rcu_grace_period: rcu_preempt
> 21343 fqsend
> rcu_preempt-9 [000] ...1 851.748487: rcu_grace_period: rcu_preempt
> 21343 fqswait
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 13/13 #P:4
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / delay
> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> # | | | |||| | |
> rcu_preempt-9 [003] d..2 851.878457: rcu_grace_period: rcu_preempt
> 21349 end
> rcu_preempt-9 [003] d..2 851.878459: rcu_grace_period: rcu_preempt
> 21349 newreq
> rcu_preempt-9 [003] ...1 851.878459: rcu_grace_period: rcu_preempt
> 21349 reqwait
> rcu_preempt-9 [003] d..2 851.878460: rcu_grace_period: rcu_preempt
> 21350 start
> rcu_preempt-9 [003] d..2 851.878461: rcu_grace_period: rcu_preempt
> 21350 cpustart
> rcu_preempt-9 [003] d..2 851.878462: rcu_grace_period_init:
> rcu_preempt 21350 0 0 7 f
> rcu_preempt-9 [003] ...1 851.878463: rcu_grace_period: rcu_preempt
> 21350 fqswait
> rcu_preempt-9 [003] d..2 851.878464: rcu_grace_period: rcu_preempt
> 21350 cpuqs
> <idle>-0 [000] dNs3 851.878482: rcu_grace_period: rcu_preempt
> 21349 cpuend
> <idle>-0 [000] dNs3 851.878483: rcu_grace_period: rcu_preempt
> 21350 cpustart
> <idle>-0 [000] dNs3 851.878484: rcu_grace_period: rcu_sched
> 20086 cpuend
> <idle>-0 [000] .N.2 851.878486: rcu_grace_period: rcu_sched
> 20086 cpuqs
> <idle>-0 [000] dN.2 851.878487: rcu_grace_period: rcu_preempt
> 21350 cpuqs
>
>
> followed by a half dozen 'empty' traces before it totally locked up.
Cool, thank you!
Could you please also send the RCU CPU stall warning messages?
Thanx, Paul
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