Re: [Tarantool-patches] [PATCH 1/1] fiber_cond: remove rlist_shift usages

[Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

On Mon, Mar 01, 2021 at 11:23:13PM +0100, Vladislav Shpilevoy wrote:
> @@ -94,7 +94,7 @@ fiber_cond_broadcast(struct fiber_cond *e)
>  {
>  	while (! rlist_empty(&e->waiters)) {
>  		struct fiber *f;
> -		f = rlist_shift_entry(&e->waiters, struct fiber, state);
> +		f = rlist_first_entry(&e->waiters, struct fiber, state);
>  		fiber_wakeup(f);
>  	}
>  }

The fiber_wakeup ignores

	if (f->flags & (FIBER_IS_READY | FIBER_IS_DEAD))
		return;

can't we hit the situation where fiber_cond_broadcast called with
dead fiber so that it won't be deleted from the list with new code?

Actually looking into fiber_loop code I see

static void
fiber_loop(MAYBE_UNUSED void *data)
{
	...
	fiber->flags |= FIBER_IS_DEAD;
	while (! rlist_empty(&fiber->wake)) {
		       struct fiber *f;
		       f = rlist_shift_entry(&fiber->wake, struct fiber,
					     state);
		       assert(f != fiber);
		       fiber_wakeup(f);
	}

so it should be safe with your patch, but just to make sure I didn't
miss something obvious.