Re: [PATCH 1/3] usage: refactor die-recursion checks

> > Right. My assumption was that we are primarily interested in protecting
> > against the die_routine. Compat functions should never be calling die.
> 
> I think the rule we have been enforcing is less strict than that.  We
> have only said that any compat function in a die handler path should
> never call die.  But maybe that's what you meant.

> The primary motivation was that Hannes Sixt had to step in and point
> out yet again that the high-level memory allocators should not be
> called in anything that could be in a die handler code path.  I was on
> the thread, but I don't remember the topic (ah, Jonathan has stepped
> in with the answer).  I do remember that I was not the only one who
> had forgotten about that rule though.

> To implement this check correctly/completely (i.e. detect recursion in
> the main thread as well as in any child threads), I think you really
> do need to use thread-local storage as you mentioned in 3/3 which
> could look something like:
> 
>    static pthread_key_t dying;
>    static pthread_once_t dying_once = PTHREAD_ONCE_INIT;
> 
>    void setup_die_counter(void)
>    {
>            pthread_key_create(&dying, NULL);
>    }
> 
>    check_die_recursion(void)
>    {
>            pthread_once(&dying_once, setup_die_counter);
>            if (pthread(getspecific(dying)) {
>                    puts("BUG: recursion...");
>                    exit(128);
>            }
> 
>            pthread_setspecific(dying, &dying);
>    }