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Date: Thu, 16 Apr 2009 01:35:34 +0200
From: Frederic Weisbecker <fweisbec@...il.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Alexander Beregalov <a.beregalov@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
Alessio Igor Bogani <abogani@...ware.it>,
Jeff Mahoney <jeffm@...e.com>,
ReiserFS Development List <reiserfs-devel@...r.kernel.org>,
Chris Mason <chris.mason@...cle.com>
Subject: Re: [tree] latest kill-the-BKL tree, v12
On Thu, Apr 16, 2009 at 01:07:36AM +0200, Ingo Molnar wrote:
>
> * Alexander Beregalov <a.beregalov@...il.com> wrote:
>
> > 2009/4/14 Ingo Molnar <mingo@...e.hu>:
> > >
> > > * Alexander Beregalov <a.beregalov@...il.com> 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 <a.beregalov@...il.com> -----
>
> Date: Wed, 15 Apr 2009 22:08:01 +0400
> From: Alexander Beregalov <a.beregalov@...il.com>
> To: linux-kernel <linux-kernel@...r.kernel.org>,
> Ingo Molnar <mingo@...e.hu>, linux-nfs@...r.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.
Thanks.
> other info that might help us debug this:
>
> 1 lock held by mount.nfs/1740:
> #0: (&type->s_umount_key#24/1){+.+.+.}, at: [<00000000004b88a0>]
> sget+0x228/0x36c
>
> stack backtrace:
> Call Trace:
> [00000000004755ac] print_circular_bug_tail+0xfc/0x10c
> [0000000000476e24] __lock_acquire+0x12f0/0x1b40
> [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
> device: '0:19': device_add
>
> ----- End forwarded message -----
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