From owner-freebsd-current  Mon Feb 11 19:45:40 2002
Delivered-To: freebsd-current@freebsd.org
Received: from newman2.bestweb.net (newman2.bestweb.net [209.94.102.67])
	by hub.freebsd.org (Postfix) with ESMTP id A1C2037B63D
	for <current@FreeBSD.ORG>; Mon, 11 Feb 2002 18:18:57 -0800 (PST)
Received: from okeeffe.bestweb.net (okeefe.bestweb.net [209.94.100.110])
	by newman2.bestweb.net (Postfix) with ESMTP
	id 46621232BB; Mon, 11 Feb 2002 21:17:57 -0500 (EST)
Received: by okeeffe.bestweb.net (Postfix, from userid 0)
	id E4CA99EFF0; Mon, 11 Feb 2002 21:12:38 -0500 (EST)
Date: Mon, 11 Feb 2002 06:32:48 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
To: Julian Elischer <julian@elischer.org>
Cc: <current@FreeBSD.ORG>
Subject: Re: final ucred patch
Message-Id: <20020212021238.E4CA99EFF0@okeeffe.bestweb.net>
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-current.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-current>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-current>
X-Loop: FreeBSD.ORG

> After comments by jhb and bde
>
> Index: i386/i386/trap.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/i386/i386/trap.c,v
> retrieving revision 1.211
> diff -u -r1.211 trap.c
> --- i386/i386/trap.c	10 Jan 2002 11:49:54 -0000	1.211
> +++ i386/i386/trap.c	10 Feb 2002 00:52:58 -0000
> @@ -256,9 +256,19 @@
>  		sticks = td->td_kse->ke_sticks;
>  		td->td_frame = &frame;
>  		KASSERT(td->td_ucred == NULL, ("already have a ucred"));
> -		PROC_LOCK(p);
> -		td->td_ucred = crhold(p->p_ucred);
> -		PROC_UNLOCK(p);
> +		if (td->td_ucred != p->p_ucred) {
> +			if (td->td_ucred) {
> +				mtx_lock(&Giant);
> +				crfree(td->td_ucred);
> +				td->td_ucred = NULL;
> +				mtx_unlock(&Giant);

See below about placement of this unlock.

> +			}
> +			if (p->p_ucred) {

How can this be NULL?  The old code didn't check.

> +				PROC_LOCK(p);
> +				td->td_ucred = crhold(p->p_ucred);
> +				PROC_UNLOCK(p);
> +			}
> +		}

The inner block is large enough and repeated enough to turn into a function.

>
>  		switch (type) {
>  		case T_PRIVINFLT:	/* privileged instruction fault */
> @@ -644,10 +654,12 @@
>  	userret(td, &frame, sticks);
>  	mtx_assert(&Giant, MA_NOTOWNED);
>  userout:
> +#ifdef	INVARIANTS
>  	mtx_lock(&Giant);
>  	crfree(td->td_ucred);
> -	mtx_unlock(&Giant);
>  	td->td_ucred = NULL;
> +	mtx_unlock(&Giant);
> +#endif
>  out:
>  	return;
>  }

I think moving the unlock is just an obfuscation.  td_ucred isn't locked
by Giant.

Bruce


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message