Re: [Tarantool-patches] [PATCH 1/4] fiber: introduce fiber.arg

[Serge Petrenko <sergepetrenko@tarantool.org>]

08.11.2020 21:03, Vladislav Shpilevoy пишет:
> Struct fiber has a member va_list f_data. It is used to forward
> arguments to the fiber function when fiber_start() is called,
> right from the caller's stack.
>
> But it is useless when fiber is started asynchronously, with
> fiber_new + fiber_wakeup. And there is no way to pass anything
> into such a fiber.
>
> This patch adds a new member 'void *arg', which shares memory with
> va_list f_data, and can be used to pass something into the fiber.
>
> The feature is going to be used by raft. Currently raft worker
> fiber works only with global variables, but soon it will need to
> have its own pointer at struct raft object. And it can't be
> started with fiber_start(), because raft code does not yield
> anywhere in its state machine.
>
> Needed for #5303

Hi! Thanks for the patch!

LGTM.

> ---
>   src/lib/core/fiber.h | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/src/lib/core/fiber.h b/src/lib/core/fiber.h
> index 539e5c8e7..08f1dd662 100644
> --- a/src/lib/core/fiber.h
> +++ b/src/lib/core/fiber.h
> @@ -565,7 +565,19 @@ struct fiber {
>   	 * See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31488
>   	 */
>   	fiber_func f;
> -	va_list f_data;
> +	union {
> +		/**
> +		 * Argument list passed when the fiber is invoked in a blocking
> +		 * way, so the caller may pass arguments from its own stack.
> +		 */
> +		va_list f_data;
> +		/**
> +		 * Fiber function argument which passed asynchronously. Can be
> +		 * used not to call fiber_start to avoid yields, but still pass
> +		 * something into the fiber.
> +		 */
> +		void *arg;
> +	};
>   	int f_ret;
>   	/** Fiber local storage. */
>   	struct {

-- 
Serge Petrenko