On Wed, Jul 26, 2017 at 04:33:40PM +0100, Jonathan Cameron wrote: > On Wed, 26 Jul 2017 15:23:15 +0100 > Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > On Wed, 26 Jul 2017 07:14:17 -0700 > > "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > > > > On Wed, Jul 26, 2017 at 01:28:01PM +0100, Jonathan Cameron wrote: > > > > On Wed, 26 Jul 2017 10:32:32 +0100 > > > > Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > > > > > > > On Wed, 26 Jul 2017 09:16:23 +0100 > > > > > Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > > > > > > > > > > On Tue, 25 Jul 2017 21:12:17 -0700 > > > > > > "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > > > > On Tue, Jul 25, 2017 at 09:02:33PM -0700, David Miller wrote: > > > > > > > > From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> > > > > > > > > Date: Tue, 25 Jul 2017 20:55:45 -0700 > > > > > > > > > > > > > > > > > On Tue, Jul 25, 2017 at 02:10:29PM -0700, David Miller wrote: > > > > > > > > >> Just to report, turning softlockup back on fixes things for me on > > > > > > > > >> sparc64 too. > > > > > > > > > > > > > > > > > > Very good! > > > > > > > > > > > > > > > > > >> The thing about softlockup is it runs an hrtimer, which seems to run > > > > > > > > >> about every 4 seconds. > > > > > > > > > > > > > > > > > > I could see where that could shake things loose, but I am surprised that > > > > > > > > > it would be needed. I ran a short run with CONFIG_SOFTLOCKUP_DETECTOR=y > > > > > > > > > with no trouble, but I will be running a longer test later on. > > > > > > > > > > > > > > > > > >> So I wonder if this is a NO_HZ problem. > > > > > > > > > > > > > > > > > > Might be. My tests run with NO_HZ_FULL=n and NO_HZ_IDLE=y. What are > > > > > > > > > you running? (Again, my symptoms are slightly different, so I might > > > > > > > > > be seeing a different bug.) > > > > > > > > > > > > > > > > I run with NO_HZ_FULL=n and NO_HZ_IDLE=y, just like you. > > > > > > > > > > > > > > > > To clarify, the symptoms show up with SOFTLOCKUP_DETECTOR disabled. > > > > > > > > > > > > > > Same here -- but my failure case happens fairly rarely, so it will take > > > > > > > some time to gain reasonable confidence that enabling SOFTLOCKUP_DETECTOR > > > > > > > had effect. > > > > > > > > > > > > > > But you are right, might be interesting to try NO_HZ_PERIODIC=y > > > > > > > or NO_HZ_FULL=y. So many possible tests, and so little time. ;-) > > > > > > > > > > > > > > Thanx, Paul > > > > > > > > > > > > > I'll be the headless chicken running around and trying as many tests > > > > > > as I can fit in. Typical time to see the failure for us is sub 10 > > > > > > minutes so we'll see how far we get. > > > > > > > > > > > > Make me a list to run if you like ;) > > > > > > > > > > > > NO_HZ_PERIODIC=y running now. > > > > > By which I mean CONFIG_HZ_PERIODIC=y > > > > > > I did get that messed up, didn't I? Sorry for my confusion! > > > > > > > > Anyhow, run for 40 minutes with out seeing a splat but my sanity check > > > > > on the NO_FULL_HZ=n and NO_HZ_IDLE=y this morning took 20 minutes so > > > > > I won't have much confidence until we are a few hours in on this. > > > > > > > > > > Anyhow, certainly looking like a promising direction for investigation! > > > > > > > > > Well it's done over 3 hours without a splat so I think it is fine with > > > > CONFIG_HZ_PERIODIC=y > > > > > > Thank you! > > > > > > If you run with SOFTLOCKUP_DETECTOR=n and NO_HZ_IDLE=y, but have a normal > > > user task waking up every few seconds on each CPU, does the problem occur? > > > (The question is whether any disturbance gets things going, or whether there > > > is something special about SOFTLOCKUP_DETECTOR=y and HZ_PERIODIC=y. > > > > > > Dave, any other ideas on what might be causing this or what might be > > > tested? > > > > > > Thanx, Paul > > > > > > > Although it's still early days (40 mins in) it looks like the issue first > > occurred between 4.10-rc7 and 4.11-rc1 (don't ask why those particular RCs) > > > > Bad as with current kernel on 4.11-rc1 and good on 4.10-rc7. > > Didn't leave it long enough. Still bad on 4.10-rc7 just took over > an hour to occur. And it is quite possible that SOFTLOCKUP_DETECTOR=y and HZ_PERIODIC=y are just greatly reducing the probability of the problem rather than completely preventing it. Still, hopefully useful information, thank you for the testing! Thanx, Paul > > Could be something different was hiding it in 4.10 though. We have a fair > > delta from mainline back then unfortunately so bisecting will be > > 'interesting'. > > > > I'll see if I can get the test you suggest running. > > > > Jonathan > > _______________________________________________ > > linuxarm mailing list > > linuxarm@xxxxxxxxxx > > http://rnd-openeuler.huawei.com/mailman/listinfo/linuxarm > -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
