Re: [Tarantool-patches] [PATCH v8 1/2] fiber: set diagnostics at madvise/mprotect failure

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Hi! Thanks for the patch!

> diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
> index 00ae8cded..f10687b29 100644
> --- a/src/lib/core/fiber.c
> +++ b/src/lib/core/fiber.c
> @@ -1007,6 +1035,8 @@ fiber_stack_watermark_create(struct fiber *fiber)
>  static void
>  fiber_stack_destroy(struct fiber *fiber, struct slab_cache *slabc)
>  {
> +	static const int mprotect_flags = PROT_READ | PROT_WRITE;
> +

Well, seems like you won't change this. Ok, since I can't do
anything about that, I have nothing to do but to say the
patchset is ok.

>  	if (fiber->stack != NULL) {
>  		VALGRIND_STACK_DEREGISTER(fiber->stack_id);
>  #if ENABLE_ASAN
> @@ -1017,7 +1047,22 @@ fiber_stack_destroy(struct fiber *fiber, struct slab_cache *slabc)
>  			guard = page_align_down(fiber->stack - page_size);
>  		else
>  			guard = page_align_up(fiber->stack + fiber->stack_size);
> -		fiber_mprotect(guard, page_size, PROT_READ | PROT_WRITE);
> +
> +		if (fiber_mprotect(guard, page_size, mprotect_flags) != 0) {
> +			/*
> +			 * FIXME: We need some intelligent handling:
> +			 * say put this slab into a queue and retry
> +			 * to setup the original protection back in
> +			 * background.
> +			 *
> +			 * Note that in case if we're called from
> +			 * fiber_stack_create() the @a mprotect_flags is

You could just say "protection flags are the same as the slab..." instead
of mentioning a variable here. If you didn't think that enum would be good
here.