Re: PROBLEM: 3.0-rc kernels unbootable since -rc3

Konrad Rzeszutek Wilk
2011-07-11T16:25:08Z

On Sun, Jul 10, 2011 at 04:14:49PM -0700, Paul E. McKenney wrote:
> On Sun, Jul 10, 2011 at 10:50:48PM +0100, julie Sullivan wrote:
> > > Very cool!  Thank you very much for the testing --
.. snip..
> And here is what I am proposing sending upstream. I have your Tested-by,

Hey Paul,

I am hitting a similar bug.
Starting udev Kernel Device Manager...
Starting Configure read-only root support...
[ 79.942067] INFO: rcu_sched_state detected stalls on CPUs/tasks: { 0} (detected by 2, t=60002 jiffies)
[ 79.942089] sending NMI to all CPUs:

when running a 3.0-rc6 under Xen as 32-bit guest (I don't see this issue
when running a 64-bit guest) and when I've more than two CPUs under the guest.

I've tried the patch below against 3.0-rc6 and it did not fix the issue.

I've also tried to use 3.0-rc3 as somewhere in thread one of the reporters mentioned
that it worked for me - but that did not help me.

The config is a Fedora Core based. The stack traces of the four CPUs look
as follow:

CPU0:
Call Trace:
[<c04023a7>] hypercall_page+0x3a7 <--
[<c0405ed5>] xen_safe_halt+0x12
[<c040ea08>] default_idle+0x5a
[<c04081a6>] cpu_idle+0x8e
[<c07da9a9>] rest_init+0x5d
[<c0a86788>] start_kernel+0x34d
[<c0a861c4>] unknown_bootoption
[<c0a860ba>] i386_start_kernel+0xa9
[<c0a895ce>] xen_start_kernel+0x55d
[<c04090b1>] sys_rt_sigreturn+0xb

CPU1 and CPU2:
Call Trace:
[<c04023a7>] hypercall_page+0x3a7 <--
[<c0405ed5>] xen_safe_halt+0x12
[<c040ea08>] default_idle+0x5a
[<c04081a6>] cpu_idle+0x8e
[<c07e5419>] cpu_bringup_and_idle+0xd

CPU3:
Call Trace:
[<c042d0f2>] task_waking_fair+0x11 <--
[<c0439a45>] try_to_wake_up+0xb2
[<c0439b0c>] default_wake_function+0x10
[<c042d4db>] __wake_up_common+0x3b
[<c042ea69>] complete+0x3e
[<c0455e14>] wakeme_after_rcu+0x10
[<c048fd58>] __rcu_process_callbacks+0x172
[<c049080f>] rcu_process_callbacks+0x20
[<c044567d>] __do_softirq+0xa2
[<c04455db>] __do_softirq
[<c040a52d>] do_softirq+0x5a

The full config is http://darnok.org/xen/config-rcu-stall
The full bootup log is http://darnok.org/xen/log-rcu-stall

Any thoughts of what I ought to try? I don't know if there is some missing functionality
in the RCU patches to work under Xen.... Any older version of Linux kernel
you would like me to try?