Re: [Tarantool-patches] [PATCH v2 1/1] fiber: extend max fiber name length to 255

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Sun, Mar 15, 2020 at 04:11:14PM +0100, Vladislav Shpilevoy wrote:
...
> diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
> index ada7972cb..359ef1187 100644
> --- a/src/lib/core/fiber.c
> +++ b/src/lib/core/fiber.c
> @@ -912,8 +912,26 @@ fiber_loop(MAYBE_UNUSED void *data)
>  void
>  fiber_set_name(struct fiber *fiber, const char *name)
>  {
> -	assert(name != NULL);
> -	snprintf(fiber->name, sizeof(fiber->name), "%s", name);
> +	size_t len = strlen(name);
> +	if (len <= FIBER_NAME_INLINE) {
> +		if (fiber->name != fiber->inline_name) {
> +			free(fiber->name);
> +			fiber->name = fiber->inline_name;
> +		}
> +	} else {
> +		if (len > FIBER_NAME_MAX)
> +			len = FIBER_NAME_MAX;
> +		char *new_name;
> +		if (fiber->name != fiber->inline_name)
> +			new_name = realloc(fiber->name, len + 1);
> +		else
> +			new_name = malloc(len + 1);
> +		if (new_name == NULL)
> +			panic("fiber_set_name() failed with OOM");
> +		fiber->name = new_name;
> +	}
> +	memcpy(fiber->name, name, len);
> +	fiber->name[len] = 0;
>  }

Thank, Vlad! I like the patch. There is only one concern I have: for
some reason we has been defining faiber name as

char name[FIBER_NAME_MAX + 1];

where FIBER_NAME_MAX = 32 and finally this expands to "char name[33];"
I'm too lazy to find who exactly introduced this but it is bloody
wrong: compiler alings members to eliminate data access penalty, thus
_actually_ it will be defined as 8 multilier, ie 40 bytes.

Thus, if you don't mind I propose make FIBER_NAME_INLINE = 40
*including* string terminating zero.

Actually we can make it on top then. Up to you. Anyway

Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>