On 08/13/11 03:53, Peter Zijlstra wrote:
> 
> Whee, I can skip release announcements too!
> 
> So no the subject ain't no mistake its not, 3.0.1-rt11 is there for the
> grabs.
> 
> Changes include (including the missing -rt10):
> 
>   - hrtimer fix that should make RT_GROUP work again
>   - RCU fixes that should make the RCU stalls go away
>   - fixes SMP=n builds after breaking them in -rt9

I have a consistent (every boot) hang on boot.  With a few
hacks to get console output, I get the

  rcu_preempt_state detected stalls on CPUs/tasks

messages in the attached console log.


The hacks are the attached patches.

   zzz_allow_console_trylock_for_sysrq
     Allows printk() to spew messages when it would otherwise
     be delayed, if oops_in_progress is true.

   zzz-turn-on-oops_in_progress
     Initializes oops_in_progress to 1 so that the boot
     printk()s and the rcu stall messages can spew forth.

   zzz-add-arm-arch_trigger_all_cpu_backtrace
     Prints the stack traces for each cpu when the rcu stalls
     are detected.  ARM does not have an NMI, so I used an
     IPI to trigger the stack trace on each cpu.  I think this
     is the reason I get a second rcu stall message immediately
     after the first one (at time 63.194937).

This is an ARM NaviEngine (out of tree, so I also have applied
a series of pages for platform support).

CONFIG_PREEMPT_RT_FULL is set.  Full config is attached.

-Frank