Messages in this thread | | | From | Jay Vosburgh <> | Subject | Re: localed stuck in recent 3.18 git in copy_net_ns? | Date | Fri, 24 Oct 2014 15:41:31 -0700 |
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Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
>On Fri, Oct 24, 2014 at 03:02:04PM -0700, Jay Vosburgh wrote: >> Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: >> [...] >> I've got an ftrace capture from unmodified -net, it looks like >> this: >> >> ovs-vswitchd-902 [000] .... 471.778441: rcu_barrier: rcu_sched Begin cpu -1 remaining 0 # 0 >> ovs-vswitchd-902 [000] .... 471.778452: rcu_barrier: rcu_sched Check cpu -1 remaining 0 # 0 >> ovs-vswitchd-902 [000] .... 471.778452: rcu_barrier: rcu_sched Inc1 cpu -1 remaining 0 # 1 >> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 0 remaining 1 # 1 >> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 1 remaining 2 # 1 >> ovs-vswitchd-902 [000] .... 471.778453: rcu_barrier: rcu_sched OnlineNoCB cpu 2 remaining 3 # 1 >> ovs-vswitchd-902 [000] .... 471.778454: rcu_barrier: rcu_sched OnlineNoCB cpu 3 remaining 4 # 1 > >OK, so it looks like your system has four CPUs, and rcu_barrier() placed >callbacks on them all.
No, the system has only two CPUs. It's an Intel Core 2 Duo E8400, and /proc/cpuinfo agrees that there are only 2. There is a potentially relevant-sounding message early in dmesg that says:
[ 0.000000] smpboot: Allowing 4 CPUs, 2 hotplug CPUs
>> ovs-vswitchd-902 [000] .... 471.778454: rcu_barrier: rcu_sched Inc2 cpu -1 remaining 4 # 2 > >The above removes the extra count used to avoid races between posting new >callbacks and completion of previously posted callbacks. > >> rcuos/0-9 [000] ..s. 471.793150: rcu_barrier: rcu_sched CB cpu -1 remaining 3 # 2 >> rcuos/1-18 [001] ..s. 471.793308: rcu_barrier: rcu_sched CB cpu -1 remaining 2 # 2 > >Two of the four callbacks fired, but the other two appear to be AWOL. >And rcu_barrier() won't return until they all fire. > >> I let it sit through several "hung task" cycles but that was all >> there was for rcu:rcu_barrier. >> >> I should have ftrace with the patch as soon as the kernel is >> done building, then I can try the below patch (I'll start it building >> now). > >Sounds very good, looking forward to hearing of the results.
Going to bounce it for ftrace now, but the cpu count mismatch seemed important enough to mention separately.
-J
--- -Jay Vosburgh, jay.vosburgh@canonical.com
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