Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754630AbZDPIwb (ORCPT ); Thu, 16 Apr 2009 04:52:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752598AbZDPIwS (ORCPT ); Thu, 16 Apr 2009 04:52:18 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:47951 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751930AbZDPIwP (ORCPT ); Thu, 16 Apr 2009 04:52:15 -0400 Date: Thu, 16 Apr 2009 10:51:53 +0200 From: Ingo Molnar To: Frederic Weisbecker Cc: Alexander Beregalov , Peter Zijlstra , linux-nfs@vger.kernel.org, netdev@vger.kernel.org, LKML , Alessio Igor Bogani , Jeff Mahoney , ReiserFS Development List , Chris Mason Subject: Re: [tree] latest kill-the-BKL tree, v12 Message-ID: <20090416085153.GC9813@elte.hu> References: <1239680065-25013-1-git-send-email-fweisbec@gmail.com> <20090414045109.GA26908@orion> <20090414090146.GH27003@elte.hu> <20090415230736.GA22710@elte.hu> <20090415233533.GA5962@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20090415233533.GA5962@nowhere> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8841 Lines: 229 * Frederic Weisbecker wrote: > On Thu, Apr 16, 2009 at 01:07:36AM +0200, Ingo Molnar wrote: > > > > * Alexander Beregalov wrote: > > > > > 2009/4/14 Ingo Molnar : > > > > > > > > * Alexander Beregalov wrote: > > > > > > > >> On Tue, Apr 14, 2009 at 05:34:22AM +0200, Frederic Weisbecker wrote: > > > >> > Ingo, > > > >> > > > > >> > This small patchset fixes some deadlocks I've faced after trying > > > >> > some pressures with dbench on a reiserfs partition. > > > >> > > > > >> > There is still some work pending such as adding some checks to ensure we > > > >> > _always_ release the lock before sleeping, as you suggested. > > > >> > Also I have to fix a lockdep warning reported by Alessio Igor Bogani. > > > >> > And also some optimizations.... > > > >> > > > > >> > Thanks, > > > >> > Frederic. > > > >> > > > > >> > Frederic Weisbecker (3): > > > >> > ? kill-the-BKL/reiserfs: provide a tool to lock only once the write lock > > > >> > ? kill-the-BKL/reiserfs: lock only once in reiserfs_truncate_file > > > >> > ? kill-the-BKL/reiserfs: only acquire the write lock once in > > > >> > ? ? reiserfs_dirty_inode > > > >> > > > > >> > ?fs/reiserfs/inode.c ? ? ? ? | ? 10 +++++++--- > > > >> > ?fs/reiserfs/lock.c ? ? ? ? ?| ? 26 ++++++++++++++++++++++++++ > > > >> > ?fs/reiserfs/super.c ? ? ? ? | ? 15 +++++++++------ > > > >> > ?include/linux/reiserfs_fs.h | ? ?2 ++ > > > >> > ?4 files changed, 44 insertions(+), 9 deletions(-) > > > >> > > > > >> > > > >> Hi > > > >> > > > >> The same test - dbench on reiserfs on loop on sparc64. > > > >> > > > >> [ INFO: possible circular locking dependency detected ] > > > >> 2.6.30-rc1-00457-gb21597d-dirty #2 > > > > > > > > I'm wondering ... your version hash suggests you used vanilla > > > > upstream as a base for your test. There's a string of other fixes > > > > from Frederic in tip:core/kill-the-BKL branch, have you picked them > > > > all up when you did your testing? > > > > > > > > The most coherent way to test this would be to pick up the latest > > > > core/kill-the-BKL git tree from: > > > > > > > > ? git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core/kill-the-BKL > > > > > > > > > > I did not know about this branch, now I am testing it and there is > > > no more problem with that testcase (dbench). > > > > > > I will continue testing. > > > > thanks for testing it! It seems reiserfs with Frederic's changes > > appears to be more stable now on your system. > > > > > Yeah, thanks a lot for this testing! > > > > > I saw your NFS circular locking kill-the-BKL problem report on LKML > > - also attached below. > > > > Hopefully someone on the Cc: list with NFS experience can point out > > the BKL assumption that is causing this. > > > > Ingo > > > > ----- Forwarded message from Alexander Beregalov ----- > > > > Date: Wed, 15 Apr 2009 22:08:01 +0400 > > From: Alexander Beregalov > > To: linux-kernel , > > Ingo Molnar , linux-nfs@vger.kernel.org > > Subject: [core/kill-the-BKL] nfs3: possible circular locking dependency > > > > Hi > > > > I have pulled core/kill-the-BKL on top of 2.6.30-rc2. > > > > device: '0:18': device_add > > > > ======================================================= > > [ INFO: possible circular locking dependency detected ] > > 2.6.30-rc2-00057-g30aa902-dirty #5 > > ------------------------------------------------------- > > mount.nfs/1740 is trying to acquire lock: > > (kernel_mutex){+.+.+.}, at: [<00000000006f32dc>] lock_kernel+0x28/0x3c > > > > but task is already holding lock: > > (&type->s_umount_key#24/1){+.+.+.}, at: [<00000000004b88a0>] sget+0x228/0x36c > > > > which lock already depends on the new lock. > > > > > > the existing dependency chain (in reverse order) is: > > > > -> #1 (&type->s_umount_key#24/1){+.+.+.}: > > [<00000000004776d0>] lock_acquire+0x5c/0x74 > > [<0000000000469f5c>] down_write_nested+0x38/0x50 > > [<00000000004b88a0>] sget+0x228/0x36c > > [<00000000005688fc>] nfs_get_sb+0x80c/0xa7c > > [<00000000004b7ec8>] vfs_kern_mount+0x44/0xa4 > > [<00000000004b7f84>] do_kern_mount+0x30/0xcc > > [<00000000004cf300>] do_mount+0x7c8/0x80c > > [<00000000004ed2a4>] compat_sys_mount+0x224/0x274 > > [<0000000000406154>] linux_sparc_syscall32+0x34/0x40 > > > > -> #0 (kernel_mutex){+.+.+.}: > > [<00000000004776d0>] lock_acquire+0x5c/0x74 > > [<00000000006f0ebc>] mutex_lock_nested+0x48/0x380 > > [<00000000006f32dc>] lock_kernel+0x28/0x3c > > [<00000000006d20ec>] rpc_wait_bit_killable+0x64/0x8c > > [<00000000006f0620>] __wait_on_bit+0x64/0xc0 > > [<00000000006f06e4>] out_of_line_wait_on_bit+0x68/0x7c > > [<00000000006d2938>] __rpc_execute+0x150/0x2b4 > > [<00000000006d2ac0>] rpc_execute+0x24/0x34 > > [<00000000006cc338>] rpc_run_task+0x64/0x74 > > [<00000000006cc474>] rpc_call_sync+0x58/0x7c > > [<00000000005717b0>] nfs3_rpc_wrapper+0x24/0xa0 > > [<0000000000572024>] do_proc_get_root+0x6c/0x10c > > [<00000000005720dc>] nfs3_proc_get_root+0x18/0x5c > > [<000000000056401c>] nfs_get_root+0x34/0x17c > > [<0000000000568adc>] nfs_get_sb+0x9ec/0xa7c > > [<00000000004b7ec8>] vfs_kern_mount+0x44/0xa4 > > [<00000000004b7f84>] do_kern_mount+0x30/0xcc > > [<00000000004cf300>] do_mount+0x7c8/0x80c > > [<00000000004ed2a4>] compat_sys_mount+0x224/0x274 > > [<0000000000406154>] linux_sparc_syscall32+0x34/0x40 > > > > > This is still the dependency between bkl and s_umount_key that has > been reported recently. I wonder if this is not a problem in the > fs layer. I should investigate on it. The problem seem to be that this NFS call context: -> #0 (kernel_mutex){+.+.+.}: [<00000000004776d0>] lock_acquire+0x5c/0x74 [<00000000006f0ebc>] mutex_lock_nested+0x48/0x380 [<00000000006f32dc>] lock_kernel+0x28/0x3c [<00000000006d20ec>] rpc_wait_bit_killable+0x64/0x8c [<00000000006f0620>] __wait_on_bit+0x64/0xc0 [<00000000006f06e4>] out_of_line_wait_on_bit+0x68/0x7c [<00000000006d2938>] __rpc_execute+0x150/0x2b4 [<00000000006d2ac0>] rpc_execute+0x24/0x34 [<00000000006cc338>] rpc_run_task+0x64/0x74 [<00000000006cc474>] rpc_call_sync+0x58/0x7c [<00000000005717b0>] nfs3_rpc_wrapper+0x24/0xa0 [<0000000000572024>] do_proc_get_root+0x6c/0x10c [<00000000005720dc>] nfs3_proc_get_root+0x18/0x5c [<000000000056401c>] nfs_get_root+0x34/0x17c [<0000000000568adc>] nfs_get_sb+0x9ec/0xa7c [<00000000004b7ec8>] vfs_kern_mount+0x44/0xa4 [<00000000004b7f84>] do_kern_mount+0x30/0xcc [<00000000004cf300>] do_mount+0x7c8/0x80c [<00000000004ed2a4>] compat_sys_mount+0x224/0x274 [<0000000000406154>] linux_sparc_syscall32+0x34/0x40 Can be called with the BKL held - and then it schedule()s with the BKL held, creating dependencies. I did the quick hack below (a year ago! :-) but indeed that's probably wrong: we just drop and then re-acquire the BKL at a very low level - inverting the dependency chain. It's not a problem of the NFS code, it's the probem of vfs_kern_mount taking the BKL. Maybe it would be better if nfs_get_sb() dropped the BKL (knowing that it's called with the BKL held) - since it does not rely on the BKL? Not rpc_wait_bit_killable(). Ingo --------------> >From 352e0d25def53e6b36234e4dc2083ca7f5d712a9 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 14 May 2008 17:31:41 +0200 Subject: [PATCH] remove the BKL: restructure NFS code the naked schedule() in rpc_wait_bit_killable() caused the BKL to be auto-dropped in the past. avoid the immediate hang in such code. Note that this still leaves some other locking dependencies to be sorted out in the NFS code. Signed-off-by: Ingo Molnar --- net/sunrpc/sched.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index 6eab9bf..e12e571 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -224,9 +224,15 @@ EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue); static int rpc_wait_bit_killable(void *word) { + int bkl = kernel_locked(); + if (fatal_signal_pending(current)) return -ERESTARTSYS; + if (bkl) + unlock_kernel(); schedule(); + if (bkl) + lock_kernel(); return 0; } -- 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/