Re: Regression: x86/tsc: Fix mark_tsc_unstable()

[Diego Viola]

On Mon, Jun 11, 2018 at 10:59 AM, Jeremy Cline <jeremy@xxxxxxxxxx> wrote:
> Hi folks,
>
> A few Fedora users have reported[0] a regression starting in v4.16.8
> where the boot will hang ~1/3 of the time with the following RCU stall
> warning:
>
> INFO: rcu_sched detected stalls on CPUs/tasks:
> o1-...!: (0 ticks this GP) idle=688/0/0 softirq=171/171 fqs=0
> o(detected by 0, t=60002 jiffies, g=-142, c=-143, q=9)
> Sending NMI from CPU 0 to CPU 1:
> NMI backtrace for cpu 1 skipped: idling at
> acpi_processor_ffh_cstate_enter+0x65/0xb0
> rcu_sched kthread starved for 60002 jiffies! g18446744073709551474
> c1844674407370955143 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 -> cpu=1
> RCU grace-period kthread stack dump:
> rcu_sched       I    0     9      2 0x80000000
> Call Trace:
>  ? __schedule+0x234/0x850
>  schedule+0x28/0x80
>  schedule_timeout+0x166/0x380
>  ? __next_timer_interrupt+0xc0/0xc0
>  rcu_gp_kthread+0x368/0x830
>  ? rcu_process_callbacks+0x4f0/0x4f0
>  kthread+0x112/0x130
>  ? kthread_create_worker_on_cpu+0x70/0x70
>  ret_from_fork+0x35/0x40
>
> A user has bisected the problem to the v4.16 commit 1ab4ca7c59d4
> ("x86/tsc: Fix mark_tsc_unstable()"). According to the reporter,
> explicitly setting "tsc=" on the kernel command line causes the boot to
> always succeed. All the users have Thinkpad T500s or T400s (Core 2 Duos)
>
> [0] https://bugzilla.redhat.com/show_bug.cgi?id=1579925
>
>
> Thanks,
> Jeremy

Everything works fine here with 4.16.8+ on my desktop with E5500 CPU.

[diego@dualcore ~]$ uname -a
Linux dualcore 4.16.13-2-ARCH #1 SMP PREEMPT Fri Jun 1 18:46:11 UTC
2018 x86_64 GNU/Linux
[diego@dualcore ~]$