From owner-cvs-src@FreeBSD.ORG Thu Mar 3 05:45:38 2005 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7091516A4CE; Thu, 3 Mar 2005 05:45:38 +0000 (GMT) Received: from freefall.freebsd.org (freefall.freebsd.org [216.136.204.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2424D43D2D; Thu, 3 Mar 2005 05:45:38 +0000 (GMT) (envelope-from davidxu@freebsd.org) Received: from [127.0.0.1] (davidxu@localhost [127.0.0.1]) by freefall.freebsd.org (8.13.1/8.13.1) with ESMTP id j235jXd2091511; Thu, 3 Mar 2005 05:45:35 GMT (envelope-from davidxu@freebsd.org) Message-ID: <4226A46B.2090704@freebsd.org> Date: Thu, 03 Mar 2005 13:45:15 +0800 From: David Xu User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.3) Gecko/20040910 X-Accept-Language: en-us, en MIME-Version: 1.0 To: David Schultz References: <200503021343.j22DhpQ3075008@repoman.freebsd.org> <200503020915.28512.jhb@FreeBSD.org> <4226446B.7020406@freebsd.org> <20050303033115.GA13174@VARK.MIT.EDU> <42269DB0.6070107@freebsd.org> <20050303052902.GA14011@VARK.MIT.EDU> In-Reply-To: <20050303052902.GA14011@VARK.MIT.EDU> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit cc: cvs-src@freebsd.org cc: src-committers@freebsd.org cc: cvs-all@freebsd.org cc: John Baldwin Subject: Re: cvs commit: src/sys/kern kern_sig.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Mar 2005 05:45:38 -0000 David Schultz wrote: >You have to worry about that anyway, though. A and B need to know >that they're not allowed to hold locks across the calls if C calls >msleep(), for instance. Anyway, your proposal if having a flag >for msleep() is basically the same as my proposal of having a >separate function. (The only difference is that adding a separate >function doesn't break the ABI.) So it sounds like we're more or >less in agreement here. > > > This is not a lock problem, this is the problem why a stack variable can not be used when thread is going to sleep, this is a rather odd behavior to me. For example, thread A stack variable address p is put on a known place, e.g, a queue, thread A unlocks the lock of the queue and sleeps, sometimes later, a producer thread B writes the data into memory pointed by p, and wake up A, that's a very simple code, here malloc is not needed at all. At the time, kernel shoudn't swap out the thread stack, any code trying to swap it out is totally broken. >>>The alternative, of course, is to just fix the code that assumes >>>that swapping doesn't exist. >>> >>> >>> >>First find all code written in such way, but it is not that easy. >> >> > >True. If we changed msleep() to disable swapping by default, then >we wouldn't have to worry about correctness problems related to >missing some. > > > >