Re: RCU lockup in the SMP idle thread, help...

[Nicolas Pitre]

On Thu, 20 Sep 2012, Linus Walleij wrote:

> On Thu, Sep 20, 2012 at 2:03 AM, Paul E. McKenney
> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> 
> > Any thoughts on the feasibility of implementing NMI-based stack backtraces
> > for ARM?
> 
> Nico's department, so let's page him.

That _could_ be done, at least in theory, with some restrictions.  

However in practice ...

> In IIRC ux500 all NMIs are reserved for the secure world, so it's
> basically a no can do. :-(

That's the main issue here: not all platforms allow FIQs ( a FIQ is the 
closest to a NMI on ARM) to be available to the operating system.

However, for where this is possible, there is a patch series from Anton 
Vorontsov implementing FIQ based KGDB support which might be useful 
here.


Nicolas
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