From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753377AbYH1Igc (ORCPT ); Thu, 28 Aug 2008 04:36:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751285AbYH1IgX (ORCPT ); Thu, 28 Aug 2008 04:36:23 -0400 Received: from pasmtpa.tele.dk ([80.160.77.114]:53684 "EHLO pasmtpA.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbYH1IgX (ORCPT ); Thu, 28 Aug 2008 04:36:23 -0400 Date: Thu, 28 Aug 2008 10:36:20 +0200 From: Jens Axboe To: Neil Brown Cc: Andrew Morton , "Rafael J. Wysocki" , jurriaan , linux-kernel@vger.kernel.org Subject: Re: 2.6.27-rc4: lots of 'in_atomic():1, irqs_disabled():0' with software-raid1 Message-ID: <20080828083620.GX20055@kernel.dk> References: <20080827170538.GA24393@amd64.of.nowhere> <200808272347.43577.rjw@sisk.pl> <20080828073324.GR20055@kernel.dk> <20080828004532.45d8b8c9.akpm@linux-foundation.org> <20080828074830.GV20055@kernel.dk> <18614.24929.952454.829021@notabene.brown> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18614.24929.952454.829021@notabene.brown> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 28 2008, Neil Brown wrote: > On Thursday August 28, jens.axboe@oracle.com wrote: > > On Thu, Aug 28 2008, Andrew Morton wrote: > > > > > > Cant sleep inside rcu_read_lock(), with CONFIG_PREEMPT_RCU=n, at least. > > > > > > Dunno if it's legal if CONFIG_PREEMPT_RCU=y. Hopefully not - that > > > would be insane. But I've failed to keep up with rcu goings-on > > > recently. > > > > Doh right, we of course can't block inside a RCU section. Then > > bitmap.c:write_sb_page() wants fixing: > > > > rcu_read_lock(); > > rdev_for_each_rcu(...) > > md_super_write(...) > > bio_alloc(GFP_NOIO, 1); > > > > Neil? > > > Yes...... > > And not only can't I call bio_alloc inside the rcu_read_lock, I also > cannot call submit_bio, as that can do a mempool alloc for a request > structure. Right, it's not the only broken part there. > I can get around that by putting the bios on the ->biolist that > md_super_wait will resubmit requests from. But I still need to > allocate those bios. > Maybe I can count how many there need to be, then allocate them and > make a list, then pass them down into md_super_write. > It's a bit ugly but it should work. > > I think I'll have to think about it a bit more. That was my initial thought as well, but the problem there is that you cannot prealloc > 1 bio without matching it with a submit_bio() as well, or you'd violate the bio_alloc() restriction on having the previous in flight before allocating a new one. -- Jens Axboe