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.
Dave
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