From owner-cvs-all Thu Jul 5 3:47:42 2001 Delivered-To: cvs-all@freebsd.org Received: from anchor-post-31.mail.demon.net (anchor-post-31.mail.demon.net [194.217.242.89]) by hub.freebsd.org (Postfix) with ESMTP id 4123737B401; Thu, 5 Jul 2001 03:47:36 -0700 (PDT) (envelope-from dfr@nlsystems.com) Received: from [62.49.251.130] (helo=herring.nlsystems.com) by anchor-post-31.mail.demon.net with esmtp (Exim 2.12 #1) id 15I6gM-0004fP-0V; Thu, 5 Jul 2001 11:48:26 +0100 Received: from herring (herring [10.0.0.2]) by herring.nlsystems.com (8.11.2/8.11.2) with ESMTP id f65AkJ730432; Thu, 5 Jul 2001 11:46:19 +0100 (BST) (envelope-from dfr@nlsystems.com) Date: Thu, 5 Jul 2001 11:46:19 +0100 (BST) From: Doug Rabson To: Matthew Jacob Cc: John Baldwin , Matt Dillon , , , Jake Burkholder Subject: Re: cvs commit: src/sys/sys systm.h condvar.h src/sys/kern kern_ In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Wed, 4 Jul 2001, Matthew Jacob wrote: > > Imagine an interrupt between the wakeup and lock release. That would give > > plenty enough time for another CPU to grab the woken process and then block on > > the lock. > > John- show some numbers with even a 32 processor SGI that this happens > all that much. Yer reachin'.... I think that all John is saying that the possibility of taking an interrupt can make the size of the window large enough for another cpu (or for preemption on this cpu) to grab the woken process. I know from the original alpha port that in a buildworld, even 1-2 instruction windows can cause races. -- Doug Rabson Mail: dfr@nlsystems.com Phone: +44 20 8348 6160 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message