Re: [Qemu-devel] [PATCH 3/9] linux-user: Don't reset a new thread's CPU

[Peter Maydell]

On 6 July 2013 01:36, Alexander Graf <address@hidden> wrote:
> When we create a new thread, there is no reason to reset it. I'm fairly sure
> the code has mostly been left in there because nobody understood why it was
> there in the first place.

We had a big discussion on this on IRC. This code is here
because of commit b4558d748, which attempted to fix a breakage
introduced when commit b55a37c9 made these CPUs no longer do
a reset as part of their cpu_init(). However, it's in the
wrong place -- this reset needs to go into cpu_copy(), so
it doesn't undo the copying work done by that function.

> Remove the reset. A new thread's kernel sided state should be identical to
> the old one's.

Just deleting the reset isn't right. We should standardize
whether we think cpu_init() ought to give you a cleanly
reset CPU or not (I think it should); until then, we should
put a cpu_reset() immediately after cpu_init() in cpu_copy().
It doesn't need to be ifdef-guarded either.

thanks
-- PMM