From: Alexandre Ratchov <alex@caoua.org>
Subject: Re: Forever loop in azalia.c
To: Ali Farzanrad <ali_farzanrad@riseup.net>
Cc: tech@openbsd.org, kettenis@openbsd.org, ratchov@openbsd.org, martijn@openbsd.org, stsp@openbsd.org
Date: Fri, 24 May 2024 12:32:11 +0200

On Fri, May 24, 2024 at 10:08:29AM +0000, Ali Farzanrad wrote:
> Hi tech@
> 
> I found this infinite loop in azalia.c:
> 
> Index: azalia.c
> ===================================================================
> RCS file: /home/cvs/src/sys/dev/pci/azalia.c,v
> diff -u -p -r1.287 azalia.c
> --- azalia.c	17 May 2024 19:43:45 -0000	1.287
> +++ azalia.c	24 May 2024 10:03:02 -0000
> @@ -701,7 +701,7 @@ azalia_intr(void *v)
>  	int ret = 0;
>  
>  	mtx_enter(&audio_lock);
> -	for (;;) {
> +	do {
>  		intsts = AZ_READ_4(az, INTSTS);
>  		if ((intsts & az->intctl) == 0 || intsts == 0xffffffff)
>  			break;
			^^^^^^

There's a break condition. Furthermore, the loop is necessary: we've
to loop (process events) as long as the INTSTS register is not zero
(ie as long as there's work to do)

> @@ -722,7 +722,7 @@ azalia_intr(void *v)
>  			azalia_rirb_intr(az);
>  			ret = 1;
>  		}
> -	}
> +	} while (0);
>  	mtx_leave(&audio_lock);
>  	return (ret);
>  }
> 
> 
> I CCed this email to everyone related to that forever loop commit.
> 
> 
> Bests,
> Ali Farzanrad
> 
>