Messages in this thread | | | Date | Sat, 14 Oct 2017 05:51:16 -0700 | From | "Paul E. McKenney" <> | Subject | Re: Bug report for RCU stalled warning [3.10.69] |
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On Thu, Oct 12, 2017 at 01:38:24PM -0700, Paul E. McKenney wrote: > [ Adding LKML on CC so that others can find this. ] > > On Wed, Oct 11, 2017 at 12:21:39PM +0800, Wang YanQing wrote: > > Hi, Paul McKenney. > > > > I have received many machine-stopped-respone reports, after reboot and > > inspect message, all of them show RCU stalled, but I can't figure out > > how to fix it. I can't update the kernel, it is the painful point, so I > > need to fix it in 3.10. I have attached four messages come from different > > cpu and broads(so I guess it is a BUG instead of hardware fault), any > > suggestion is welcome. > > The first step is of course to report this to your distro, as they are > the ones who do the care and feeding of such old kernels. Please include > the information below in that report, as it might help your distro find > and fix the problem. > > It looks like the stalled CPU is idle, and that the activity resulting > from the stall-warning message gets things going again. Callbacks are > being processed, so no OOM. But you are getting the splat every 60 > seconds. The system has only two CPUs, and is x86. > > If you cannot upgrade the kernel, my ability to help is limited. And the > diagnostics printed with the v3.10 CPU stall warnings are also quite > limited. However, there are some things you could try as workarounds: > > 1. Check to make sure that the rcu_sched kthread is getting > the CPU time that it needs. Preventing this kthread from > running would create exactly this output, assuming that > the stall warning got it going again temporarily. > > 2. It looks like the disturbance of the RCU CPU stall warning > is getting things going again. Try artificially providing > this disturbance, for example, by running a usermode program > or script that runs on each CPU in turn, then sleeps for > (say) five seconds. > > 3. If you can reconfigure your kernel, try building with > CONFIG_RCU_FAST_NO_HZ=n.
And if you can reconfigure kernel, in v3.10, building with CONFIG_RCU_CPU_STALL_INFO and CONFIG_RCU_CPU_STALL_VERBOSE will provide more information on the CPUs and tasks stalling the grace period.
Thanx, Paul
> 4. Was the system running reliably on some earlier version? > If so, consider reverting back to that version, and include > the version information in your report to your distro. If > your distro provides individual patches, you should consider > bisecting so as to locate the offending patch. > > Good luck with it! > > Thanx, Paul
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