Messages in this thread |  | | Date | Thu, 23 Oct 2014 08:33:33 -0700 | From | "Paul E. McKenney" <> | Subject | Re: localed stuck in recent 3.18 git in copy_net_ns? |
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On Thu, Oct 23, 2014 at 05:27:50AM -0700, Paul E. McKenney wrote: > On Thu, Oct 23, 2014 at 09:09:26AM +0300, Yanko Kaneti wrote: > > On Wed, 2014-10-22 at 16:24 -0700, Paul E. McKenney wrote: > > > On Thu, Oct 23, 2014 at 01:40:32AM +0300, Yanko Kaneti wrote: > > > > On Wed-10/22/14-2014 15:33, Josh Boyer wrote: > > > > > On Wed, Oct 22, 2014 at 2:55 PM, Paul E. McKenney > > > > > <paulmck@linux.vnet.ibm.com> wrote: > > > > > > [ . . . ] > > > > > > > > > Don't get me wrong -- the fact that this kthread appears to > > > > > > have > > > > > > blocked within rcu_barrier() for 120 seconds means that > > > > > > something is > > > > > > most definitely wrong here. I am surprised that there are no > > > > > > RCU CPU > > > > > > stall warnings, but perhaps the blockage is in the callback > > > > > > execution > > > > > > rather than grace-period completion. Or something is > > > > > > preventing this > > > > > > kthread from starting up after the wake-up callback executes. > > > > > > Or... > > > > > > > > > > > > Is this thing reproducible? > > > > > > > > > > I've added Yanko on CC, who reported the backtrace above and can > > > > > recreate it reliably. Apparently reverting the RCU merge commit > > > > > (d6dd50e) and rebuilding the latest after that does not show the > > > > > issue. I'll let Yanko explain more and answer any questions you > > > > > have. > > > > > > > > - It is reproducible > > > > - I've done another build here to double check and its definitely > > > > the rcu merge > > > > that's causing it. > > > > > > > > Don't think I'll be able to dig deeper, but I can do testing if > > > > needed. > > > > > > Please! Does the following patch help? > > > > Nope, doesn't seem to make a difference to the modprobe ppp_generic > > test > > Well, I was hoping. I will take a closer look at the RCU merge commit > and see what suggests itself. I am likely to ask you to revert specific > commits, if that works for you.
Well, rather than reverting commits, could you please try testing the following commits?
11ed7f934cb8 (rcu: Make nocb leader kthreads process pending callbacks after spawning)
73a860cd58a1 (rcu: Replace flush_signals() with WARN_ON(signal_pending()))
c847f14217d5 (rcu: Avoid misordering in nocb_leader_wait())
For whatever it is worth, I am guessing this one.
a53dd6a65668 (rcutorture: Add RCU-tasks tests to default rcutorture list)
If any of the above fail, this one should also fail.
Also, could you please send along your .config?
Thanx, Paul
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