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From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
In-reply-to: <1466375313-7562-9-git-send-email-sergey.fedorov@linaro.org>
Date: Tue, 28 Jun 2016 17:18:10 +0100
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Subject: Re: [Qemu-devel] [RFC 8/8] tcg: Make tb_flush() thread safe
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To: Sergey Fedorov <sergey.fedorov@linaro.org>
Cc: qemu-devel@nongnu.org, Peter Crosthwaite <crosthwaite.peter@gmail.com>, patches@linaro.org, Paolo Bonzini <pbonzini@redhat.com>, Sergey Fedorov <serge.fdrv@gmail.com>, Richard Henderson <rth@twiddle.net>


Sergey Fedorov <sergey.fedorov@linaro.org> writes:

> From: Sergey Fedorov <serge.fdrv@gmail.com>
>
> Use async_safe_run_on_cpu() to make tb_flush() thread safe.
>
> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
> ---
>  translate-all.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/translate-all.c b/translate-all.c
> index 3f402dfe04f5..09b1d0b0efc3 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -832,7 +832,7 @@ static void page_flush_tb(void)
>
>  /* flush all the translation blocks */
>  /* XXX: tb_flush is currently not thread safe */
           ^^^

The comment belies a lack of confidence ;-)

> -void tb_flush(CPUState *cpu)
> +static void do_tb_flush(CPUState *cpu, void *data)
>  {
>  #if defined(DEBUG_FLUSH)
>      printf("qemu: flush code_size=%ld nb_tbs=%d avg_tb_size=%ld\n",
> @@ -861,6 +861,11 @@ void tb_flush(CPUState *cpu)
>      tcg_ctx.tb_ctx.tb_flush_count++;
>  }
>
> +void tb_flush(CPUState *cpu)
> +{
> +    async_safe_run_on_cpu(cpu, do_tb_flush, NULL);
> +}
> +
>  #ifdef DEBUG_TB_CHECK
>
>  static void
> @@ -1163,9 +1168,8 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>   buffer_overflow:
>          /* flush must be done */
>          tb_flush(cpu);
> -        /* cannot fail at this point */
> -        tb = tb_alloc(pc);
> -        assert(tb != NULL);
> +        mmap_unlock();
> +        cpu_loop_exit(cpu);
>      }
>
>      gen_code_buf = tcg_ctx.code_gen_ptr;


--
Alex Bennée