On Sun, Jul 30, 2023 at 08:54:46PM -0700, Paul E. McKenney wrote: > On Thu, Jul 27, 2023 at 09:22:52PM -0700, Guenter Roeck wrote: > > On 7/27/23 13:33, Paul E. McKenney wrote: > > [ ... ] > > > > > So which of the following Kconfig options is defined in your .config? > > > CONFIG_TASKS_RCU, CONFIG_TASKS_RUDE_RCU, and CONFIG_TASKS_TRACE_RCU. > > > > > > > Only CONFIG_TASKS_RCU. I added another log message after call_rcu_tasks(). > > It never returns from that function. > > > > [ 1.168993] Running RCU synchronous self tests > > [ 1.169219] Running RCU synchronous self tests > > [ 1.285795] smpboot: CPU0: Intel Xeon Processor (Cascadelake) (family: 0x6, model: 0x55, stepping: 0x6) > > [ 1.302827] RCU Tasks: Setting shift to 0 and lim to 1 rcu_task_cb_adjust=1. > > [ 1.304526] Running RCU Tasks wait API self tests > > > > ... and then nothing for at least 10 minutes (then I gave up and stopped the test). > > > > Qemu command line: > > > > qemu-system-x86_64 -kernel \ > > arch/x86/boot/bzImage -M q35 -cpu Cascadelake-Server -no-reboot \ > > -snapshot -device e1000e,netdev=net0 -netdev user,id=net0 -m 256 \ > > -drive file=rootfs.iso,format=raw,if=ide,media=cdrom \ > > --append "earlycon=uart8250,io,0x3f8,9600n8 panic=-1 slub_debug=FZPUA root=/dev/sr0 rootwait console=ttyS0 noreboot" \ > > -d unimp,guest_errors -nographic -monitor none > > > > Again, this doesn't happen all the time. With Cascadelake-Server > > I see it maybe once every 5 boot attempts. I tried with qemu v8.0 > > and v8.1. Note that it does seem to happen with various CPU types, > > only for some it seems to me more likely to happen (so maybe the > > CPU type was a red herring). It does seem to depend on the system > > load, and happen more often if the system is under heavy load. > > Hmmm... What kernel are you using as your qemu/KVM hypervisor? Never mind, I now see your bisection result. Good show, thank you!!! Thanx, Paul > And I echo Joel's requests for your .config file. > > Thanx, Paul
