From owner-cvs-src@FreeBSD.ORG Mon Mar 12 16:16:17 2007 Return-Path: X-Original-To: cvs-src@freebsd.org Delivered-To: cvs-src@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 94CFD16A402; Mon, 12 Mar 2007 16:16:17 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (66-23-211-162.clients.speedfactory.net [66.23.211.162]) by mx1.freebsd.org (Postfix) with ESMTP id BAB7413C43E; Mon, 12 Mar 2007 16:16:16 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from localhost.corp.yahoo.com (john@localhost [127.0.0.1]) (authenticated bits=0) by server.baldwin.cx (8.13.8/8.13.8) with ESMTP id l2CGGBgU062821; Mon, 12 Mar 2007 11:16:12 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: "Attilio Rao" Date: Mon, 12 Mar 2007 11:14:59 -0400 User-Agent: KMail/1.9.1 References: <200703092241.l29Mf2Ds062856@repoman.freebsd.org> <20070310205236.GA9185@garage.freebsd.pl> <3bbf2fe10703101611r60d6e1c5o8ef5fcf309fbf0e3@mail.gmail.com> In-Reply-To: <3bbf2fe10703101611r60d6e1c5o8ef5fcf309fbf0e3@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200703121114.59859.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [127.0.0.1]); Mon, 12 Mar 2007 11:16:12 -0500 (EST) X-Virus-Scanned: ClamAV 0.88.3/2823/Mon Mar 12 04:55:20 2007 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Pawel Jakub Dawidek , cvs-all@freebsd.org Subject: Re: cvs commit: src/share/man/man9 Makefile condvar.9 lock.9 mi_switch.9 mtx_pool.9 mutex.9 rwlock.9 sleep.9 sleepqueue.9 sx.9 thread_exit.9 src/sys/kern kern_synch.c src/sys/sys mutex.h rwlock.h sleepqueue.h sx.h systm.h X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 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: Mon, 12 Mar 2007 16:16:17 -0000 On Saturday 10 March 2007 19:11, Attilio Rao wrote: > 2007/3/10, Pawel Jakub Dawidek : > > On Sat, Mar 10, 2007 at 12:44:26PM +0100, Attilio Rao wrote: > > > 2007/3/9, John Baldwin : > > > >I don't have a date set for removing msleep(), esp. given it's wide use. > > > >I would like to remove it and all the spl*() functions in 8.0 if we can > > > >swing it. > > > > > > > >I also have patches to let condition variables work with rwlocks and sx > > > >locks, but the current implementation results in an API "explosion" > > > >since each of the cv_*wait*() functions grows a cv_*wait*_rw() version for > > > >rwlocks and a cv_*waut*_sx() version for use with sx locks. One possibility > > > >would be to just cast the lock argument to (struct lock_object *) since all > > > >of our locks have a lock_object as the first member, but then you use having > > > >the compiler do type checking, and I'm really not willing to give up on > > > >that. Too easy to have evil bugs that way. I suppose we could use some > > > >evil macro that used typeof() but that would be very gcc specific? > > > > > > > >I guess one other possibility is to standardize on the field name for > > > >the lock_object, calling it lo_object instead of mtx_object, rw_object, > > > >sx_object, etc. Anyone else have any ideas? > > > > > > What about adding a new function like: > > > > > > static __inline struct lock_object * > > > mtx_export_lc(struct mtx *m) > > > { > > > > > > return (&m->mtx_object); > > > } > > > > > > to be per-interface (so having sx_export_lc() and rw_export_lc() too) > > > and than using in this way: > > > > > > static struct mtx foo_lock; > > > static struct cv foo_cv; > > > ... > > > > > > mtx_lock(&foo_lock); > > > ... > > > cv_wait(&foo_cv, mtx_export_lc(&foo_lock)); > > > > > > (obviously using new struct lock_object methods you added for locking/unlocking) > > > > > > It sounds reasonable to you? > > > > This is ugly. If we really need to provide information about which type > > of lock we are using, I'd probably prefer cv_wait_(). > > > > What about something like this: > > > > #define cv_wait(cv, lock) do { > > switch (LO_CLASSINDEX((struct lock_object *)(lock))) { > > case 1: > > cv_wait_mtx(cv, lock); > > break; > > case 2: > > cv_wait_sx(cv, lock); > > break; > > case 3: > > cv_wait_rw(cv, lock); > > break; > > default: > > panic("Invalid lock."); > > } > > } while (0) > > This is exactly what John is trying to avoid. > You have however to export cv_wait_*() & friends in the public > namespace and at this point you don't need such wrapper. > > I know it is not so elegant, but the other solutions are uglier. > Having a function returning the lock object per-primitive is the most > suitable, IMHO. No, that's more typing than _rw and _sx. Here is what I want to happen if possible: cv_wait(cv, mtx); cv_wait(cv, rw); cv_wait(cv, sx); and have the the compiler figure it out. Basically, trying to shoehorn some C++ into C since mtx, rw, and sx are sub-classes of 'lock_object'. :) That is, I'd like it to do something like this: #define cv_wait(cv, lock) do { \ if (typeof(lock) == (struct mtx *)) \ _cv_wait(cv, &lock->mtx_object); \ else if (typeof(lock) == (struct rwlock *)) \ _cv_wait(cv, &lock->rw_object); \ else if (typeof(lock) == (struct sx *)) \ _cv_wait(cv, &lock->sx_object); \ else \ compile_error; \ } while (0) So you still get type checking, etc. I'm thinking maybe the simplest thing to do is to rename 'mtx_object', 'rw_object', and 'sx_object' fields to all be 'lock_object' and then do this: #define cv_wait(cv, lock) _cv_wait((cv), &(lock)->lock_object) -- John Baldwin