From owner-freebsd-current Mon Feb 11 20:47:19 2002 Delivered-To: freebsd-current@freebsd.org Received: from mail11.speakeasy.net (mail11.speakeasy.net [216.254.0.211]) by hub.freebsd.org (Postfix) with ESMTP id 93FD337BFE5 for ; Mon, 11 Feb 2002 20:13:20 -0800 (PST) Received: (qmail 27696 invoked from network); 12 Feb 2002 04:13:11 -0000 Received: from unknown (HELO laptop.baldwin.cx) ([65.91.152.149]) (envelope-sender ) by mail11.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 12 Feb 2002 04:13:11 -0000 Message-ID: X-Mailer: XFMail 1.4.0 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <3C6886C4.B2B08C5B@mindspring.com> Date: Mon, 11 Feb 2002 23:13:02 -0500 (EST) From: John Baldwin To: Terry Lambert Subject: Re: ucred holding patch, BDE version Cc: Julian Elischer , bde@freebsd.org, current@freebsd.org, Alfred Perlstein Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On 12-Feb-02 Terry Lambert wrote: > John Baldwin wrote: >> Yes, calling free() without Giant is about as good as calling fdrop() >> without >> Giant Alfred. :) > > Alfred would be right, for per processor memory pools. 8-). > >> >> And on the way into the system it does: >> >> lock process >> >> crhold() (which includes mutex ops) >> >> unlock process >> > >> > This isn't needed, at least afaik. >> >> Not strictly for the comparison as Julian and Terry pointed out since the >> race >> can occur anyway (i.e., you don't need the lock to see if p_ucred changed), >> however, if you are actually doing a crhold(), you want to make sure p_ucred >> isn't stale, so you need the proc lock. > > No. If you _depend_ on the frequency of change being low, > you can do this with only atomic reference counts. See the > pseudo code in my other posting, in direct response to you. Yes, the broken code with the race condition that can corrupt random kernel structures long enough to trigger a panic or break a condition test in a branch or loop. I saw that, yes. > -- Terry -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message