Date:	Tue, 12 Jul 2011 08:58:48 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ronny Meeus <ronny.meeus@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] [PATCH] Fix deadlock in af_packet while stressing raw
 ethernet socket interface

Le mardi 12 juillet 2011 à 08:38 +0200, Ronny Meeus a écrit :
> On Tue, Jul 12, 2011 at 5:27 AM, David Miller <davem@...emloft.net> wrote:
> > From: Ronny Meeus <ronny.meeus@...il.com>
> > Date: Sat, 11 Jun 2011 07:04:09 +0200
> >
> >> I was running a test: 1 application was sending raw Ethernet packets
> >> on a physical looped interface while a second application was
> >> receiving packets, so the latter application receives each packet 2
> >> times (once while sending from the context of the first application
> >> and a second time while receiving from the hardware).  After some
> >> time, the test blocks due to a spinlock reentrance issue in
> >> af_packet. Both the sending application and the softIRQ receiving
> >> packets enter the spinlock code. After applying the patch below, the
> >> issue is resolved.
> >>
> >> Signed-off-by: Ronny Meeus <ronny.meeus@...il.com>
> >
> > The packet receive hooks should always be called with software
> > interrupts disabled, it is a bug if this is not happening.  Your
> > patch should not be necessary at all.
> >
> >
> 
> Can you be a bit more specific on where the software interrupts should
> be disabled?
> 
> Below you find the information I get after switching on the spin_lock
> issue detection in the kernel.
> In this run also I-PIPE was active but this issue is also seen with
> I-PIPE disabled.
> 

This seems a bug, but in softirq handling in your arch

> [   96.450034] BUG: spinlock recursion on CPU#0, send_eth_socket/1907
> [   96.540451]  lock: eaeb8c9c, .magic: dead4ead, .owner:
> send_eth_socket/1907, .owner_cpu: 0
> [   96.656060] Call Trace: (unreliable)0161000 success=90] [c000789c]
> show_stack+0x78/0x18c160001
> [   96.827988] [efff3dd0] [c01e2a50] spin_bug+0xa8/0xc0=0000162000 succ
> [   96.920712] [efff3df0] [c01e2b9c] do_raw_spin_lock+0x70/0x1c4ount=0000163000
> [   97.022823] [efff3e20] [c0388d88] _raw_spin_lock+0x10/0x2001
> [   97.121800] [efff3e30] [c03391a0] tpacket_rcv+0x274/0x61c164001
> [   97.219733] [efff3e80] [c02d5970] __netif_receive_skb+0x1a8/0x36c0000165001
> [   97.326001] [efff3eb0] [c02d6234] netif_receive_skb+0x98/0xacess=0000166001
> [   97.427060] [efff3ee0] [c029e6c4] ingress_rx_default_dqrr+0x42c/0x4b8
> [   97.504194] [efff3f10] [c02ba524] qman_poll_dqrr+0x1e0/0x284
> [   97.571948] [efff3f50] [c029ff3c] dpaa_eth_poll+0x34/0xd0
> [   97.636579] [efff3f70] [c02d6514] net_rx_action+0xc0/0x1e8
> [   97.702256] [efff3fa0] [c0034d28] __do_softirq+0x138/0x210
> [   97.767928] [efff3ff0] [c0010128] call_do_softirq+0x14/0x24
> [   97.834641] [ec479a90] [c0004a00] do_softirq+0xb4/0xec

We got an IRQ, and we start do_softirq() from irq_exit()

> [   97.896148] [ec479ab0] [c0034a44] irq_exit+0x60/0xb8
> [   97.955573] [ec479ac0] [c000a490] __ipipe_do_IRQ+0x88/0xc0
> [   98.021253] [ec479ae0] [c0070214] __ipipe_sync_stage+0x1f0/0x27c
> [   98.093176] [ec479b20] [c0009f28] __ipipe_handle_irq+0x1b8/0x1e8
> [   98.165106] [ec479b50] [c000a210] __ipipe_grab_irq+0x18c/0x1bc
> [   98.234947] [ec479b80] [c0011520] __ipipe_ret_from_except+0x0/0xc
> [   98.307915] --- Exception: 501 at __packet_get_status+0x48/0x70
> [   98.307920]     LR = __packet_get_status+0x44/0x70
> [   98.436082] [ec479c40] [00000578] 0x578 (unreliable)
> [   98.495524] [ec479c50] [c0338360] packet_lookup_frame+0x48/0x70
> [   98.566405] [ec479c60] [c03391b4] tpacket_rcv+0x288/0x61c

Here we were in BH disabled section, since dev_queue_xmit() contains :

	rcu_read_lock_bh()


> [   98.631037] [ec479cb0] [c02d762c] dev_hard_start_xmit+0x164/0x588
> [   98.704003] [ec479cf0] [c0338d6c] packet_sendmsg+0x8c4/0x988
> [   98.771758] [ec479d70] [c02c3838] sock_sendmsg+0x90/0xb4
> [   98.835348] [ec479e40] [c02c4420] sys_sendto+0xdc/0x120
> [   98.897891] [ec479f10] [c02c57d0] sys_socketcall+0x148/0x210
> [   98.965648] [ec479f40] [c001084c] ret_from_syscall+0x0/0x3c
> [   99.032361] --- Exception: c01 at 0x48051f00
> [   99.032365]     LR = 0x4808e030
> [  100.563009] BUG: spinlock lockup on CPU#0, send_eth_socket/1907, eaeb8c9c
> [  100.644283] Call Trace:
> [  100.673480] [efff3db0] [c000789c] show_stack+0x78/0x18c (unreliable)
> [  100.749589] [efff3df0] [c01e2c94] do_raw_spin_lock+0x168/0x1c4
> [  100.819430] [efff3e20] [c0388d88] _raw_spin_lock+0x10/0x20
> [  100.885102] [efff3e30] [c03391a0] tpacket_rcv+0x274/0x61c
> [  100.949733] [efff3e80] [c02d5970] __netif_receive_skb+0x1a8/0x36c
> [  101.022699] [efff3eb0] [c02d6234] netif_receive_skb+0x98/0xac
> [  101.091497] [efff3ee0] [c029e6c4] ingress_rx_default_dqrr+0x42c/0x4b8
> [  101.168628] [efff3f10] [c02ba524] qman_poll_dqrr+0x1e0/0x284
> [  101.236385] [efff3f50] [c029ff3c] dpaa_eth_poll+0x34/0xd0
> [  101.301016] [efff3f70] [c02d6514] net_rx_action+0xc0/0x1e8
> [  101.366692] [efff3fa0] [c0034d28] __do_softirq+0x138/0x210
> [  101.432364] [efff3ff0] [c0010128] call_do_softirq+0x14/0x24
> [  101.499078] [ec479a90] [c0004a00] do_softirq+0xb4/0xec
> [  101.560585] [ec479ab0] [c0034a44] irq_exit+0x60/0xb8
> [  101.620003] [ec479ac0] [c000a490] __ipipe_do_IRQ+0x88/0xc0
> [  101.685678] [ec479ae0] [c0070214] __ipipe_sync_stage+0x1f0/0x27c
> [  101.757601] [ec479b20] [c0009f28] __ipipe_handle_irq+0x1b8/0x1e8
> [  101.829523] [ec479b50] [c000a210] __ipipe_grab_irq+0x18c/0x1bc
> [  101.899363] [ec479b80] [c0011520] __ipipe_ret_from_except+0x0/0xc
> [  101.972333] --- Exception: 501 at __packet_get_status+0x48/0x70
> [  101.972338]     LR = __packet_get_status+0x44/0x70
> [  102.100490] [ec479c40] [00000578] 0x578 (unreliable)
> [  102.159929] [ec479c50] [c0338360] packet_lookup_frame+0x48/0x70
> [  102.230810] [ec479c60] [c03391b4] tpacket_rcv+0x288/0x61c
> [  102.295442] [ec479cb0] [c02d762c] dev_hard_start_xmit+0x164/0x588
> [  102.368407] [ec479cf0] [c0338d6c] packet_sendmsg+0x8c4/0x988
> [  102.436162] [ec479d70] [c02c3838] sock_sendmsg+0x90/0xb4
> [  102.499747] [ec479e40] [c02c4420] sys_sendto+0xdc/0x120
> [  102.562296] [ec479f10] [c02c57d0] sys_socketcall+0x148/0x210
> [  102.630052] [ec479f40] [c001084c] ret_from_syscall+0x0/0x3c
> [  102.696773] --- Exception: c01 at 0x48051f00
> [  102.696777]     LR = 0x4808e030
> 
> Ronny
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