[Qemu-devel] Multithreaded ARM regression from 0d101938

[David Gilbert]

Hi,
  I've just filed bug 823902 ( https://bugs.launchpad.net/qemu/+bug/823902 )
which is a mutlthreaded user mode ARM crash that goes away if I revert
0d101938 ( tcg: Reload local variables after return from longjmp ).

It's actually a bit more complicated than that, in that:
   1) It fails reliably on 32bit Lucid with that commit
   2) It works reliably on 32bit Lucid without that commit
   3) It fails reliably on 64bit Oneiric or Natty with that commit
   4) It works mostly on 64bit Oneiric without that commit.

(By mostly I'm talking in run it 10 times and it fails a couple)

Peter Maydell has suggested a few things; and we've tried using a local
volatile copy of env in cpu_exec which seems to work fine on 32bit Lucid
and helps a bit on 64bit Oneiric but has a much higher failure rate than
just reverting 823902 - which is all a bit confusing.

My guess is I'm seeing multiple bugs but haven't quite nailed why/how.

Dave