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Yuriy N. Shkandybin | 5 Mar 21:17
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PROBLEM: 2.6.20 pptp server lookup

Hello.

Already several kernel releases i've expirienced different lockups of  vpn 
(pptp) server.
There is aroud 200  ppp connections at moment.
With kernel debug i was able to retrive next information:

First:
Showing all locks held in the system:
1 lock held by agetty/4486:
 #0:  (&tty->atomic_read_lock){--..}, at: [<c01d4e6f>] read_chan+0x41a/0x60b
1 lock held by agetty/4487:
 #0:  (&tty->atomic_read_lock){--..}, at: [<c01d4e6f>] read_chan+0x41a/0x60b
1 lock held by agetty/4488:
 #0:  (&tty->atomic_read_lock){--..}, at: [<c01d4e6f>] read_chan+0x41a/0x60b
2 locks held by pptpctrl/4500:
 #0:  (&tty->atomic_write_lock){--..}, at: [<c01d0f8f>] tty_write+0x83/0x1d0
 #1:  (&ap->recv_lock){....}, at: [<c02241fe>] 
ppp_asynctty_receive+0x2e/0x710

=============================================
BUG: spinlock lockup on CPU#1, pppd/4504, df5048c4
 [<c01c42c6>] _raw_spin_lock+0x100/0x134
 [<c0223f03>] ppp_async_ioctl+0xa7/0x1d0
 [<c0221b7c>] ppp_ioctl+0xa5/0xbff
 [<c012f2a5>] down_read+0x29/0x3a
 [<c0223e5c>] ppp_async_ioctl+0x0/0x1d0
 [<c0221ba5>] ppp_ioctl+0xce/0xbff
 [<c029b78f>] _spin_unlock+0x14/0x1c
 [<c014a22a>] do_wp_page+0x256/0x4ba
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Mrs Felicia Hines | 6 Mar 20:45
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IN HIS LOVE/GET BACK TO ME

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Jarek Poplawski | 9 Mar 14:10
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Re: [Bugme-new] [Bug 8132] New: pptp server lockup in ppp_asynctty_receive()

On Fri, Mar 09, 2007 at 11:40:04AM +0300, Yuriy N. Shkandybin wrote:
...
> .config is at
> http://bugzilla.kernel.org/attachment.cgi?id=10660&action=view
> Also all information i've provied was recieved by serial console and it's 
> not hand writing.
> 
> I've checked logs and right before lockup there is oops in syslog
> Mar  5 21:50:44 vpn2 skb_under_panic: text:c02248a2 len:207 put:1 
> head:db96e22c data:db96e22b tail:db96e2fa end:db96e82c dev:<NULL>

This looks like a real problem with skb and maybe with
dev->hard_header_len. I see you are using vlan module,
so maybe there is some interaction? I don't know ppp
enough, so I CC this message to the ppp list.
I'm not sure HZ change will cure this forever (maybe
some packets are going to the wrong dev?).

If you're willing to experiment, you can try to edit
"include/linux/ppp_defs.h" and change it like this:

#define PPP_HDRLEN	8
#define PPP_MRU		1496

and "include/linux/if_ppp.h":

#define PPP_MTU		1496

plus mru/mtu in your pppd config (and recompile).
(Continue reading)

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Yuriy N. Shkandybin | 19 Mar 08:49

Re: [Bug 8132] New: pptp server lockup in ppp_asynctty_receive()

I've changed kernel to rc4 and completely changed hardware.
Now this is

I've got new trace, but this is another problem as i can see and connected 
with pppoe

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.21-rc4 #1
-------------------------------------------------------
pppd/8926 is trying to acquire lock:
 (&vlan_netdev_xmit_lock_key){-...}, at: [<c0265486>] 
dev_queue_xmit+0x247/0x2f1

but task is already holding lock:
 (&pch->downl){-+..}, at: [<c0230c72>] ppp_channel_push+0x19/0x9a

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&pch->downl){-+..}:
       [<c013642b>] __lock_acquire+0xe62/0x1010
       [<c0136642>] lock_acquire+0x69/0x83
       [<c02afc13>] _spin_lock_bh+0x30/0x3d
       [<c022f715>] ppp_push+0x5a/0x9a
       [<c022fb40>] ppp_xmit_process+0x2e/0x511
       [<c0231a05>] ppp_write+0xb8/0xf2
       [<c015ec26>] vfs_write+0x7f/0xba
       [<c015f158>] sys_write+0x3d/0x64
(Continue reading)

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Jarek Poplawski | 28 Mar 10:19
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[PATCH] ppp_generic: lockdep warning Re: [Bug 8132] New: pptp server lockup ...

On Mon, Mar 19, 2007 at 10:49:12AM +0300, Yuriy N. Shkandybin wrote:
> I've changed kernel to rc4 and completely changed hardware.
> Now this is
> 
> I've got new trace, but this is another problem as i can see and connected 
> with pppoe
> 
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.21-rc4 #1
> -------------------------------------------------------
> pppd/8926 is trying to acquire lock:
> (&vlan_netdev_xmit_lock_key){-...}, at: [<c0265486>] 
> dev_queue_xmit+0x247/0x2f1
> 
> but task is already holding lock:
> (&pch->downl){-+..}, at: [<c0230c72>] ppp_channel_push+0x19/0x9a
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #3 (&pch->downl){-+..}:
>       [<c013642b>] __lock_acquire+0xe62/0x1010
>       [<c0136642>] lock_acquire+0x69/0x83
>       [<c02afc13>] _spin_lock_bh+0x30/0x3d
>       [<c022f715>] ppp_push+0x5a/0x9a
>       [<c022fb40>] ppp_xmit_process+0x2e/0x511
>       [<c0231a05>] ppp_write+0xb8/0xf2
(Continue reading)

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