From owner-cvs-all Sat Feb 23 14:12:24 2002 Delivered-To: cvs-all@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 0A68D37B404; Sat, 23 Feb 2002 14:12:19 -0800 (PST) Received: (from dillon@localhost) by apollo.backplane.com (8.11.6/8.9.1) id g1NMCI041812; Sat, 23 Feb 2002 14:12:18 -0800 (PST) (envelope-from dillon) Date: Sat, 23 Feb 2002 14:12:18 -0800 (PST) From: Matthew Dillon Message-Id: <200202232212.g1NMCI041812@apollo.backplane.com> To: Alfred Perlstein Cc: John Baldwin , Seigo Tanimura , cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/coda coda_venus.c src/sys/compat/linprocfs References: <200202232030.g1NKU4m87533@freefall.freebsd.org> <20020223204610.GG80761@elvis.mu.org> <200202232056.g1NKuKf41350@apollo.backplane.com> <20020223212005.GK80761@elvis.mu.org> 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 : :I've also asked john to implement a sleephold()/sleepdrop() functionaity. : :the premise is this: : :As you've noticed there's a bunch of code in sys/kern and sys/vm that :has comments to the effect of: : "this shouldn't block, but i'm not sure" : :Well, since for the most part blocking occurs rarely, what you do is :keep a nested count in the proc struct that records weather or not you :can sleep. : :Basically you have a td->td_sleephold that starts at zero, sleephold() :will td->td_sleephold++, and sleepdrop() will td->td_sleephold-- :as well as check for < 0. I'm fairly sure that the only time we can't block occurs while we are holding a leaf mutex. The MTX_LEAF flag in the thread may be sufficient. After all, why else would you not be able to sleep? :Then for invariants you add to all functions that may block something :like mightsleep(); at the entrance to the function. Anyone calling :into this function with a td->td_sleephold > 0 will trigger an :assertion and panic. : :As far as further assertions, I've brought this up with John and :he's ok with it, I just haven't had the time to implement it. : :I think he'd be ok with deltas but he's heard enough of my ideas :for invariants, I guess i just need to get my hands dirty with it. :) : :-- :-Alfred Perlstein [alfred@freebsd.org] -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message