Messages in this thread Patch in this message | | | Date | Fri, 24 Oct 2014 10:20:09 -0700 | From | "Paul E. McKenney" <> | Subject | Re: localed stuck in recent 3.18 git in copy_net_ns? |
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On Fri, Oct 24, 2014 at 08:09:31PM +0300, Yanko Kaneti wrote: > On Fri-10/24/14-2014 09:54, Paul E. McKenney wrote: > > On Fri, Oct 24, 2014 at 07:29:43PM +0300, Yanko Kaneti wrote: > > > On Fri-10/24/14-2014 08:40, Paul E. McKenney wrote: > > > > On Fri, Oct 24, 2014 at 12:08:57PM +0300, Yanko Kaneti wrote: > > > > > On Thu-10/23/14-2014 15:04, Paul E. McKenney wrote: > > > > > > On Fri, Oct 24, 2014 at 12:45:40AM +0300, Yanko Kaneti wrote: > > > > > > > > > > > > > > On Thu, 2014-10-23 at 13:05 -0700, Paul E. McKenney wrote: > > > > > > > > On Thu, Oct 23, 2014 at 10:51:59PM +0300, Yanko Kaneti wrote: > > > > [ . . . ] > > > > > > > Ok, unless I've messsed up something major, bisecting points to: > > > > > > > > > > 35ce7f29a44a rcu: Create rcuo kthreads only for onlined CPUs > > > > > > > > > > Makes any sense ? > > > > > > > > Good question. ;-) > > > > > > > > Are any of your online CPUs missing rcuo kthreads? There should be > > > > kthreads named rcuos/0, rcuos/1, rcuos/2, and so on for each online CPU. > > > > > > Its a Phenom II X6. With 3.17 and linux-tip with 35ce7f29a44a reverted, the rcuos are 8 > > > and the modprobe ppp_generic testcase reliably works, libvirt also manages > > > to setup its bridge. > > > > > > Just with linux-tip , the rcuos are 6 but the failure is as reliable as > > > before. > > > Thank you, very interesting. Which 6 of the rcuos are present? > > Well, the rcuos are 0 to 5. Which sounds right for a 6 core CPU like this > Phenom II.
Ah, you get 8 without the patch because it creates them for potential CPUs as well as real ones. OK, got it.
> > > Awating instructions: :) > > > > Well, I thought I understood the problem until you found that only 6 of > > the expected 8 rcuos are present with linux-tip without the revert. ;-) > > > > I am putting together a patch for the part of the problem that I think > > I understand, of course, but it would help a lot to know which two of > > the rcuos are missing. ;-) > > Ready to test
Well, if you are feeling aggressive, give the following patch a spin. I am doing sanity tests on it in the meantime.
Thanx, Paul
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diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 29fb23f33c18..927c17b081c7 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2546,9 +2546,13 @@ static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) rdp->nocb_leader = rdp_spawn; if (rdp_last && rdp != rdp_spawn) rdp_last->nocb_next_follower = rdp; - rdp_last = rdp; - rdp = rdp->nocb_next_follower; - rdp_last->nocb_next_follower = NULL; + if (rdp == rdp_spawn) { + rdp = rdp->nocb_next_follower; + } else { + rdp_last = rdp; + rdp = rdp->nocb_next_follower; + rdp_last->nocb_next_follower = NULL; + } } while (rdp); rdp_spawn->nocb_next_follower = rdp_old_leader; }
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