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Date: Wed, 27 Feb 2013 10:17:04 +1100
From: Stephen Rothwell <sfr@canb.auug.org.au>
To: Mark Jackson <mpfj-list@mimc.co.uk>
Cc: linux-next@vger.kernel.org, linux-mtd@lists.infradead.org,
        David Woodhouse <dwmw2@infradead.org>,
        lkml <linux-kernel@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: linux-next: JFFS2 deadlock
Message-Id: <20130227101704.90466ae6df78ab9b3aa4ba22@canb.auug.org.au>
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Hi Mark,

On Tue, 26 Feb 2013 11:54:56 +0000 Mark Jackson <mpfj-list@mimc.co.uk> wrot=
e:
>
> Just tested the current next-20130226 on a custom AM335X board, and I rec=
eived the JFFS2 deadlock shown below.

Is this new today?  is it reproducible? Does if ail for Linus' tree?

Al, could this be something to do with the new stuff in the vfs tree?

> Regards
> Mark JACKSON
> ---
> [    3.250349] jffs2: notice: (1) jffs2_build_xattr_subsystem: complete b=
uilding xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref =
(0 dead, 0 orphan) found.
> [    3.268364] VFS: Mounted root (jffs2 filesystem) readonly on device 31=
:6.
> [    3.277233] devtmpfs: mounted
> [    3.280982] Freeing init memory: 332K
> [    3.706697]
> [    3.708306] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> [    3.714804] [ INFO: possible circular locking dependency detected ]
> [    3.721398] 3.8.0-next-20130226-dirty #10 Not tainted
> [    3.726708] -------------------------------------------------------
> [    3.733297] rcS/686 is trying to acquire lock:
> [    3.737969]  (&mm->mmap_sem){++++++}, at: [<c00f0af4>] might_fault+0x3=
c/0x90
> [    3.745437]
> [    3.745437] but task is already holding lock:
> [    3.751569]  (&f->sem){+.+.+.}, at: [<c023d128>] jffs2_readdir+0x44/0x=
1a8
> [    3.758748]
> [    3.758748] which lock already depends on the new lock.
> [    3.758748]
> [    3.767348]
> [    3.767348] the existing dependency chain (in reverse order) is:
> [    3.775215]
> -> #1 (&f->sem){+.+.+.}:
> [    3.779184]        [<c0092df0>] lock_acquire+0x9c/0x104
> [    3.784701]        [<c04b76e4>] mutex_lock_nested+0x3c/0x334
> [    3.790666]        [<c023d950>] jffs2_readpage+0x20/0x44
> [    3.796261]        [<c00d9d38>] __do_page_cache_readahead+0x2a0/0x2cc
> [    3.803050]        [<c00da004>] ra_submit+0x28/0x30
> [    3.808187]        [<c00d179c>] filemap_fault+0x304/0x458
> [    3.813884]        [<c00f0c58>] __do_fault+0x6c/0x490
> [    3.819203]        [<c00f3c5c>] handle_pte_fault+0xb0/0x6f0
> [    3.825071]        [<c00f433c>] handle_mm_fault+0xa0/0xd4
> [    3.830755]        [<c04bbdcc>] do_page_fault+0x2a0/0x3d4
> [    3.836449]        [<c000845c>] do_DataAbort+0x30/0x9c
> [    3.841861]        [<c04ba2a4>] __dabt_svc+0x44/0x80
> [    3.847089]        [<c0289c34>] __clear_user_std+0x1c/0x64
> [    3.852877]
> -> #0 (&mm->mmap_sem){++++++}:
> [    3.857393]        [<c00927ec>] __lock_acquire+0x1d70/0x1de0
> [    3.863353]        [<c0092df0>] lock_acquire+0x9c/0x104
> [    3.868855]        [<c00f0b18>] might_fault+0x60/0x90
> [    3.874174]        [<c011bc3c>] filldir+0x5c/0x158
> [    3.879230]        [<c023d1c0>] jffs2_readdir+0xdc/0x1a8
> [    3.884823]        [<c011becc>] vfs_readdir+0x98/0xb4
> [    3.890144]        [<c011bfcc>] sys_getdents+0x74/0xd0
> [    3.895554]        [<c0013820>] ret_fast_syscall+0x0/0x3c
> [    3.901251]
> [    3.901251] other info that might help us debug this:
> [    3.901251]
> [    3.909668]  Possible unsafe locking scenario:
> [    3.909668]
> [    3.915892]        CPU0                    CPU1
> [    3.920652]        ----                    ----
> [    3.925411]   lock(&f->sem);
> [    3.928451]                                lock(&mm->mmap_sem);
> [    3.934688]                                lock(&f->sem);
> [    3.940376]   lock(&mm->mmap_sem);
> [    3.943965]
> [    3.943965]  *** DEADLOCK ***
> [    3.943965]
> [    3.950196] 2 locks held by rcS/686:
> [    3.953952]  #0:  (&type->i_mutex_dir_key){+.+.+.}, at: [<c011be90>] v=
fs_readdir+0x5c/0xb4
> [    3.962686]  #1:  (&f->sem){+.+.+.}, at: [<c023d128>] jffs2_readdir+0x=
44/0x1a8
> [    3.970320]
> [    3.970320] stack backtrace:
> [    3.974930] [<c001b158>] (unwind_backtrace+0x0/0xf0) from [<c008f29c>]=
 (print_circular_bug+0x1d0/0x2dc)
> [    3.984815] [<c008f29c>] (print_circular_bug+0x1d0/0x2dc) from [<c0092=
7ec>] (__lock_acquire+0x1d70/0x1de0)
> [    3.994975] [<c00927ec>] (__lock_acquire+0x1d70/0x1de0) from [<c0092df=
0>] (lock_acquire+0x9c/0x104)
> [    4.004494] [<c0092df0>] (lock_acquire+0x9c/0x104) from [<c00f0b18>] (=
might_fault+0x60/0x90)
> [    4.013376] [<c00f0b18>] (might_fault+0x60/0x90) from [<c011bc3c>] (fi=
lldir+0x5c/0x158)
> [    4.021802] [<c011bc3c>] (filldir+0x5c/0x158) from [<c023d1c0>] (jffs2=
_readdir+0xdc/0x1a8)
> [    4.030502] [<c023d1c0>] (jffs2_readdir+0xdc/0x1a8) from [<c011becc>] =
(vfs_readdir+0x98/0xb4)
> [    4.039477] [<c011becc>] (vfs_readdir+0x98/0xb4) from [<c011bfcc>] (sy=
s_getdents+0x74/0xd0)
> [    4.048270] [<c011bfcc>] (sys_getdents+0x74/0xd0) from [<c0013820>] (r=
et_fast_syscall+0x0/0x3c)

--=20
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au

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