From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751094AbWFXUaU (ORCPT ); Sat, 24 Jun 2006 16:30:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751095AbWFXUaU (ORCPT ); Sat, 24 Jun 2006 16:30:20 -0400 Received: from einhorn.in-berlin.de ([192.109.42.8]:30888 "EHLO einhorn.in-berlin.de") by vger.kernel.org with ESMTP id S1751094AbWFXUaT (ORCPT ); Sat, 24 Jun 2006 16:30:19 -0400 X-Envelope-From: stefanr@s5r6.in-berlin.de Message-ID: <449DA08A.10209@s5r6.in-berlin.de> Date: Sat, 24 Jun 2006 22:28:58 +0200 From: Stefan Richter User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040914 X-Accept-Language: de, en MIME-Version: 1.0 To: Arjan van de Ven CC: linux1394-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 2.6.17-mm1 4/3] ieee1394: convert ieee1394_transactions from semaphores to waitqueue References: <449BEBFB.60302@s5r6.in-berlin.de> <200606230904.k5N94Al3005245@shell0.pdx.osdl.net> <30866.1151072338@warthog.cambridge.redhat.com> <449D7A53.4080605@s5r6.in-berlin.de> <1151172766.3181.75.camel@laptopd505.fenrus.org> In-Reply-To: <1151172766.3181.75.camel@laptopd505.fenrus.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: (0.894) AWL,BAYES_50 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Arjan van de Ven wrote: > On Sat, 2006-06-24 at 19:45 +0200, Stefan Richter wrote: >>following semaphores remain in the ieee1394 subsystem: >> >>highlevel.c: hl_drivers_sem (RW semaphore) >>nodemgr.c: subsys.rwsem (driver core's RW semaphores) >>raw1394.c: fi->complete_sem (completion semaphore) > can this last one move to an actual completion? That would get rid of it > nicely ;) Hmm. There are dozens of points in raw1394 which call __queue_complete_req() which up()s the semaphore. ("fi" is the private_data of a struct file. Multiple outstanding requests may be associated with a file.) Then there are two places which wait on the semaphore: raw1394_read(), called when somebody reads /dev/raw1394: if (file->f_flags & O_NONBLOCK) { if (down_trylock(&fi->complete_sem)) return -EAGAIN; } else { if (down_interruptible(&fi->complete_sem)) return -ERESTARTSYS; } raw1394_release(), called when somebody closes (releases) /dev/raw1394: done = 0; while (!done) { /* free all complete requests */ /* set "done" if there are no more pending requests */ if (!done) down_interruptible(&fi->complete_sem); } /* cleanup, free fi */ It looks like fi->complete_sem is a actually a counting semaphore. It could perhaps be replaced by a wait queue plus an atomic counter. There is even already a wait queue in "fi" for use with poll_wait() via raw1394_poll(). -- Stefan Richter -=====-=-==- -==- ==--- http://arcgraph.de/sr/