next-20130128 lockdep whinge in sys_swapon()

next-20130128 lockdep whinge in sys_swapon()

[Valdis Kletnieks]

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Seen in my linux-next dmesg.  I'm suspecting commit ac07b1ffc:

commit ac07b1ffc27d575013041fb5277dab02c661d9c2
Author: Shaohua Li <shli@kernel.org>
Date:   Thu Jan 24 13:13:50 2013 +1100

    swap: add per-partition lock for swapfile

as (a) it was OK in -20130117, and (b) 'git blame mm/swapfile.c | grep 2013'
shows that commit as the vast majority of changes.

[   42.498669] INFO: trying to register non-static key.
[   42.498670] the code is fine but needs lockdep annotation.
[   42.498671] turning off the locking correctness validator.
[   42.498674] Pid: 1035, comm: swapon Not tainted 3.8.0-rc5-next-20130128 #52
[   42.498675] Call Trace:
[   42.498681]  [<ffffffff81073dc8>] register_lock_class+0x103/0x2ad
[   42.498685]  [<ffffffff812493ad>] ? __list_add_rcu+0xc4/0xdf
[   42.498688]  [<ffffffff81075573>] __lock_acquire+0x108/0xd63
[   42.498691]  [<ffffffff810b482b>] ? trace_preempt_on+0x12/0x2f
[   42.498695]  [<ffffffff81608e6e>] ? sub_preempt_count+0x31/0x43
[   42.498699]  [<ffffffff810fda36>] ? sys_swapon+0x6f9/0x9d9
[   42.498701]  [<ffffffff810764f2>] lock_acquire+0xc7/0x14a
[   42.498703]  [<ffffffff810fda62>] ? sys_swapon+0x725/0x9d9
[   42.498706]  [<ffffffff81605023>] _raw_spin_lock+0x34/0x41
[   42.498708]  [<ffffffff810fda62>] ? sys_swapon+0x725/0x9d9
[   42.498710]  [<ffffffff810fda62>] sys_swapon+0x725/0x9d9
[   42.498712]  [<ffffffff8107520a>] ? trace_hardirqs_on_caller+0x149/0x165
[   42.498715]  [<ffffffff8160be92>] system_call_fastpath+0x16/0x1b
[   42.498719] Adding 2097148k swap on /dev/mapper/vg_blackice-swap.  Priority:-1 extents:1 across:2097148k

Somebody care to sprinkle the appropriate annotations on that code?

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Re: next-20130128 lockdep whinge in sys_swapon()

[Minchan Kim]

Hello,


On Thu, Jan 31, 2013 at 01:45:14PM -0500, Valdis Kletnieks wrote:
> Seen in my linux-next dmesg.  I'm suspecting commit ac07b1ffc:
> 
> commit ac07b1ffc27d575013041fb5277dab02c661d9c2
> Author: Shaohua Li <shli@kernel.org>
> Date:   Thu Jan 24 13:13:50 2013 +1100
> 
>     swap: add per-partition lock for swapfile
> 
> as (a) it was OK in -20130117, and (b) 'git blame mm/swapfile.c | grep 2013'
> shows that commit as the vast majority of changes.
> 
> [   42.498669] INFO: trying to register non-static key.
> [   42.498670] the code is fine but needs lockdep annotation.
> [   42.498671] turning off the locking correctness validator.
> [   42.498674] Pid: 1035, comm: swapon Not tainted 3.8.0-rc5-next-20130128 #52
> [   42.498675] Call Trace:
> [   42.498681]  [<ffffffff81073dc8>] register_lock_class+0x103/0x2ad
> [   42.498685]  [<ffffffff812493ad>] ? __list_add_rcu+0xc4/0xdf
> [   42.498688]  [<ffffffff81075573>] __lock_acquire+0x108/0xd63
> [   42.498691]  [<ffffffff810b482b>] ? trace_preempt_on+0x12/0x2f
> [   42.498695]  [<ffffffff81608e6e>] ? sub_preempt_count+0x31/0x43
> [   42.498699]  [<ffffffff810fda36>] ? sys_swapon+0x6f9/0x9d9
> [   42.498701]  [<ffffffff810764f2>] lock_acquire+0xc7/0x14a
> [   42.498703]  [<ffffffff810fda62>] ? sys_swapon+0x725/0x9d9
> [   42.498706]  [<ffffffff81605023>] _raw_spin_lock+0x34/0x41
> [   42.498708]  [<ffffffff810fda62>] ? sys_swapon+0x725/0x9d9
> [   42.498710]  [<ffffffff810fda62>] sys_swapon+0x725/0x9d9
> [   42.498712]  [<ffffffff8107520a>] ? trace_hardirqs_on_caller+0x149/0x165
> [   42.498715]  [<ffffffff8160be92>] system_call_fastpath+0x16/0x1b
> [   42.498719] Adding 2097148k swap on /dev/mapper/vg_blackice-swap.  Priority:-1 extents:1 across:2097148k
> 
> Somebody care to sprinkle the appropriate annotations on that code?

Could you test this patch?

>From 81cae17c55ade897a7e06b01c864f1c250b40f8b Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Mon, 4 Feb 2013 10:43:32 +0900
Subject: [PATCH] mm: Get rid of lockdep whinge on sys_swapon

[1] forgot to initialize spin_lock so lockdep is whingeing
about it. This patch fixes it.

[1] 0f181e0e4, swap: add per-partition lock for swapfile

Cc: Shaohua Li <shli@kernel.org>
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 mm/swapfile.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index dfaff5f..ac190d6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1857,6 +1857,7 @@ static struct swap_info_struct *alloc_swap_info(void)
 	p->flags = SWP_USED;
 	p->next = -1;
 	spin_unlock(&swap_lock);
+	spin_lock_init(&p->lock);
 
 	return p;
 }
-- 
1.8.1.1


-- 
Kind regards,
Minchan Kim

Re: next-20130128 lockdep whinge in sys_swapon()

[Valdis.Kletnieks]

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On Mon, 04 Feb 2013 10:46:38 +0900, Minchan Kim said:

> Could you test this patch?
>
> From 81cae17c55ade897a7e06b01c864f1c250b40f8b Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@kernel.org>
> Date: Mon, 4 Feb 2013 10:43:32 +0900
> Subject: [PATCH] mm: Get rid of lockdep whinge on sys_swapon
>
> [1] forgot to initialize spin_lock so lockdep is whingeing
> about it. This patch fixes it.
>
> [1] 0f181e0e4, swap: add per-partition lock for swapfile
>
> Cc: Shaohua Li <shli@kernel.org>
> Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

I applied this to a next-20130128, and lockdep doesn't complain about
swapon().  Feel free to add a 'Tested-By:' to the patch and push it
upstream...


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