Re: [Qemu-devel] [PATCH] linux-user: Move cpu_clone_regs() and cpu_set_tls() into linux-user

[Peter Maydell]

On 25 June 2013 14:56, Richard Henderson <address@hidden> wrote:
> On 06/25/2013 03:35 AM, Peter Maydell wrote:
>> (and maybe even actually get all targets
>> up to having NPTL enabled, since it's mostly just implementing
>> the two functions being moved here for x86, sparc, openrisc.
>
> There's far more to it than that for x86.  You've got to add
> support for all of the locked arithmetic instructions.

I agree, but given that really multithreaded guest binaries
are not supported properly for any target (because of locking
issues in TCG etc) it seems like at least being able to compile
with the NPTL support turned on would be worthwhile, since it
means that clone() works and the basic x86 binaries that
currently fail would work a bit better.

> We currently have several hacks for atomic operations in
> linux-user, usually involving some escape into the cpu loop that
> pauses the other threads.  This as opposed to assuming some
> atomic support on behalf of the host...
>
> It's a mess.

No argument there. (I know the ARM atomics are implemented
in a broken way, for example.)

thanks
-- PMM