On Mon, Aug 03, 2020 at 10:04:01AM +0200, Kurt Kanzenbach wrote: > On Thu Jul 30 2020, Vladimir Oltean wrote: > > On Thu, Jul 30, 2020 at 09:23:44AM +0200, Kurt Kanzenbach wrote: > >> On Wed Jul 29 2020, Vladimir Oltean wrote: > >> > For more context, here is my original report of the issue: > >> > https://lkml.org/lkml/2020/6/4/1062 > >> > > >> > Just like you, I could not reproduce the RCU stalls and system hang on a > >> > 5.6-rt kernel, just on mainline and derivatives, using the plain > >> > defconfig. > >> > > >> > The issue is not specific to Layerscape or i.MX8, but rather I was able > >> > to see the same behavior on Marvell Armada 37xx as well as Qualcomm > >> > MSM8976. > >> > > >> > So, while of course I agree that disabling IRQ time accounting for arm64 > >> > isn't a real solution, it isn't by far an exaggerated proposal either. > >> > Nonetheless, the patch is just a RFC and should be treated as such. We > >> > are at a loss when it comes to debugging this any further and we would > >> > appreciate some pointers. > >> > >> Yeah, sure. I'll try to reproduce this issue first. So it triggers with: > >> > >> * arm64 > >> * mainline, not -rt kernel > >> * opened serial console > >> * irq accounting enabled > >> > >> Anything else? > >> > >> Thanks, > >> Kurt > > > > Thanks for giving a helping hand, Kurt. The defconfig should be enough. > > In the interest of full disclosure, the only arm64 device on which we > > didn't reproduce this was the 16-core LX2160A. But we did reproduce on > > that with maxcpus=1 though. And also on msm8976 with all 8 cores booted. > > Just mentioning this in case you're testing on a 16-core system, you > > might want to reduce the number a bit. > > OK. I've reproduced it on a Marvell Armada SoC with v5.6 mainline. See > splats below. Running with irq time accounting enabled, kills the > machine immediately. However, I'm not getting the possible deadlock > warnings in 8250 as you did. So that might be unrelated. >
Yes, the console lockdep warnings are unrelated. They are discussed here: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=vamw_vdafc...@mail.gmail.com/ > Unfortunately I have no idea what to debug here. > > Thanks, > Kurt So, this means we could submit a formal version of this patch? :) Thanks, -Vladimir
