From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752084AbaHaTbn (ORCPT ); Sun, 31 Aug 2014 15:31:43 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59457 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751449AbaHaTbl (ORCPT ); Sun, 31 Aug 2014 15:31:41 -0400 Date: Sun, 31 Aug 2014 12:31:40 -0700 From: Greg KH To: Arjan van de Ven Cc: Dmitry Torokhov , "Luis R. Rodriguez" , falcon@meizu.com, tiwai@suse.de, tj@kernel.org, linux-kernel@vger.kernel.org, oleg@redhat.com, akpm@linux-foundation.org, penguin-kernel@i-love.sakura.ne.jp, joseph.salisbury@canonical.com, bpoirier@suse.de, "Luis R. Rodriguez" Subject: Re: [RFC v1 0/3] driver-core: add asynch module loading support Message-ID: <20140831193140.GA12678@kroah.com> References: <1409475800-17573-1-git-send-email-mcgrof@do-not-panic.com> <540334B2.7000009@linux.intel.com> <20140831175040.GA17827@core.coreip.homeip.net> <5403767E.1020107@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5403767E.1020107@linux.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 31, 2014 at 12:24:46PM -0700, Arjan van de Ven wrote: > >>before we added the current async approach the approach of async init calls was tried > >>At the time, Linus hated it and he was right, it was not the right thing. > >> > >>What is different this time to make this the right thing to do ? > > > >Because otherwise drivers still have to do this, but open code it. Let's say I > >have a long operations (i.e. for some touchpads it takes about 2 secs to reset > >and configure it). I can offload that part into async_schedule() so it does not > >stop initialization of the rest of the system (why would I want to delay > >initializing of USB or storage system until touchpad is ready?) but if that > >initialization fails we end up with partially bound driver and device that is > >not really operable. I would very much prefer async and sync cases be the same > >- if probe() fails the driver is not bound to the device. > > > >I think it is wrong to make async probing system-wide, but driver opt-in shoudl > >be fine and right thing to do. > > > > I am completely fine if we make basically an async wrapper for > pci_register_driver() and friends.. that would be convenient I suppose. > > (but then again, in reality very few drivers take real time to init... most already > do the heavy work in open(). Not all can, sure, but if you look at a bootgraph.pl > graph of a typical boot it's only a few that matter). > And many drivers need to register with a subsystem, and there's some ordering around that, > and that's why we ended up with the async cookie stuff, so that you can do the > heavy work in parallel, but order near the end at registeration-with-the-subsystem time. > > But doing this on an initcall level was wrong back then, and I have yet to hear > a reason why it would be right this time. It's still wrong, it's not what I was thinking about when talking this over with Luis and Dmitry, I think something got lost in the translation... thanks, greg k-h