Re: [Jack-Devel] Stack preallocation issues

On Mon, Mar 14, 2011 at 08:14:04PM +0200, Sampo Savolainen wrote:
> On Mon, Mar 14, 2011 at 2:24 PM, torbenh <[hidden]> wrote:
> >
> > > It *has* to be in a separate function to work as expected.
> >
> > and we need to prevent that function from being inlined.
> > until i havent found the preferred way to do this, you should probably
> > deactivate that code.
> 
> 
> Wouldn't using a function pointer be good enough? It's perhaps not the most
> elegant approach, but it should guarantee the function is not inlined. (a
> patch proposal is attached)

i am currently trying to prevent the optimizer from optimizing the array
away. thats not too hard on gcc-4.4 ... but gcc-4.5 is way smarter.

> 
> 
>  Sampo

> Index: libjack/thread.c
> ===================================================================
> --- libjack/thread.c	(revision 4191)
> +++ libjack/thread.c	(working copy)
> @@ -99,6 +99,19 @@
>  #endif /* USE_CAPABILITIES */
>  }	
>  
> +static void
> +jack_thread_touch_stack()
> +{
> +	char buf[JACK_THREAD_STACK_TOUCH];
> +	int i;
> +
> +	for (i = 0; i < JACK_THREAD_STACK_TOUCH; i++) {
> +		buf[i] = (char) (i & 0xff);
> +	}
> +}
> +
> +static void (* ptr_jack_thread_touch_stack)() = jack_thread_touch_stack;
> +
>  static void*
>  jack_thread_proxy (void* varg)
>  {
> @@ -107,13 +120,8 @@
>  	void* warg;
>  	jack_client_t* client = arg->client;
>  
> -	char buf[JACK_THREAD_STACK_TOUCH];
> -	int i;
> +	ptr_jack_thread_touch_stack();
>  
> -	for (i = 0; i < JACK_THREAD_STACK_TOUCH; i++) {
> -                buf[i] = (char) (i & 0xff);
> -	}
> -
>  	if (arg->realtime) {
>  		maybe_get_capabilities (client);
>  		jack_acquire_real_time_scheduling (pthread_self(), arg->priority);
> 


-- 
torben Hohn

1300188177.31229_0.ltw:2,a <20110315112233.GA4583 at siel dot b>