Re: [Qemu-devel] [PATCH 09/22] exec-all: shrink tb->invalid to uint8_t

[Emilio G. Cota]

On Wed, Jul 12, 2017 at 13:06:23 -1000, Richard Henderson wrote:
> You've got a problem here in that you're not including CF_COUNT_MASK in the
> hash and you dropped the flush when changing to parallel_cpus = true.  That
> means you could find an old TB with CF_COUNT > 1.
> 
> Not required for this patch set, but what I'd like to see eventually is
> 
>   (1) cpu_exec_step merged into cpu_exec_step_atomic for clarity.
>   (2) callers of tb_gen_code add in CF_PARALLEL as needed; do not
>       pick it up from parallel_cpus within tb_gen_code.
>   (3) target/*/translate.c uses CF_PARALLEL instead of parallel_cpus.
>   (4) cpu_exec_step_atomic does the tb lookup and code gen outside
>       of the start_exclusive/end_exclusive lock.

I have implemented these for v2, which is almost ready to go. However,
just noticed that tcg-op.c also checks parallel_cpus to decide whether
to emit a real atomic or a non-atomic op. Should we export the two
flavours of these ops to targets, since targets are the ones that can
check CF_PARALLEL? Or perhaps set a bit in the now-per-thread *tcg_ctx?

You can see the current v2 here:
  https://github.com/cota/qemu/tree/multi-tcg-v2-2017-07-15

Thanks,

                Emilio