Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S271122AbTHCKIn (ORCPT ); Sun, 3 Aug 2003 06:08:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S271123AbTHCKIn (ORCPT ); Sun, 3 Aug 2003 06:08:43 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:56220 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S271122AbTHCKIk (ORCPT ); Sun, 3 Aug 2003 06:08:40 -0400 Date: Sun, 3 Aug 2003 12:08:37 +0200 From: Jens Axboe To: Benjamin Herrenschmidt Cc: Alan Cox , Bartlomiej Zolnierkiewicz , linux-kernel mailing list Subject: Re: IDE locking problem Message-ID: <20030803100837.GQ7920@suse.de> References: <1059900149.3524.84.camel@gaston> <20030803100447.GO7920@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030803100447.GO7920@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1571 Lines: 37 On Sun, Aug 03 2003, Jens Axboe wrote: > On Sun, Aug 03 2003, Benjamin Herrenschmidt wrote: > > Hi Alan & Bart ! > > > > While fixing my hotswap media-bay IDE controller for 2.6, I found > > a locking problem with IDE (again ? :) in ide_unregister_hw. Basically > > the problem is that it calls blk_cleanup_queue(), which is unsafe to > > call with a lock held (it will call flush_workqueue() at one point). > > Other side effect, flush_workqueue() will re-enable IRQs, thus allowing > > us to get an IRQ while holding the spinlock -> double lock, but that's > > just a side effect of calling flush_workqueue in that context. > > Irk someone made blk_cleanup_queue() non-atomic. I blame Andrew. And now > it looks like it's impossible to make it atomic again :/. Not very nice, > imo it's preferable to keep such unregister functions atomic. > > > So the call to blk_cleanup_queue() shall be moved outside of the > > spinlock. I don't know much about the BIO details, is it possible > > to first unregister_blkdev, then only call blk_cleanup_queue() ? That > > That should work, yes. > > > would help making sure we don't get a request sneaking in ? > > Hmm not really, there's still a chance that could happen. and unregister_blkdev() itself isn't even atomic. So I guess IDE does need fixing anyways. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/