Re: [Qemu-devel] [PATCH V3 01/11] atomic: introduce atomic operations

[Jamie Lokier]

Peter Maydell wrote:
> On 19 September 2012 14:32, Jamie Lokier <address@hidden> wrote:
> > However, someone may run QEMU on a kernel before 2.6.32, which isn't
> > that old.  (E.g. my phone is running 2.6.28).
> 
> NB that ARM kernels that old have other amusing bugs, such
> as not saving the floating point registers when invoking
> signal handlers.

Hi Peter,

It's not that old (< 3 years).  Granted that's not a nice one, but I'm
under the impression it occurs only when the signal handler uses (VFP
hardware) floating point.  I.e. most programs don't do that, they keep
the signal handlers simple (probably including QEMU).

(I've read about other platforms that have similar issues using
floating point in signal handlers; best avoided.)

Anyway, people are running those kernels, someone will try to run QEMU
on it unless...

> I would be happy for QEMU to just say "your  kernel is too old!"...

I'd be quite happy with that as well, if you want to put a check in
and refuse to run (like Glibc does).

Less happy with obscure, rare failures of atomicity that are
practically undebuggable, and easily fixed.

Cheers,
-- Jamie