Re: [Qemu-devel] [Bug 932487] [NEW] win32: git rev 59f971d crashes when accessing disk (coroutine issue)

[Kevin Wolf]

Am 16.02.2012 10:34, schrieb Stefan Hajnoczi:
> This is interesting because the code is a straightforward usage of
> coroutines:
> 
> co = qemu_coroutine_create(bdrv_rw_co_entry);
> qemu_coroutine_enter(co, &rwco);   <--- boom
> 
> Please make test-coroutine and try ./test-coroutine.  That performs
> some sanity checks.
> 
> I haven't had time to look in depth yet but perhaps this worked in the
> past and you could bisect it to find the commit that broke it?

Remember that I saw a similar crash a while ago? It was definitely a
NULL pointer access somewhere inside SwitchToFiber. I can't remember
exactly what came out of it, but I think you and Paolo couldn't
reproduce it and I ran out of time for debugging win32 stuff.

If I was to debug this, the first thing I would try is that I would dump
co->fiber (or actually I seem to remember it was some data structure
that is only pointed to by a field in co->fiber) immediately after the
coroutine is created (I think it was still okay then) and set a
watchpoint on it.

Kevin