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Date:	Fri, 17 Jan 2014 23:16:04 -0800 (PST)
From:	dormando <dormando@...ia.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: Re: ipv4_dst_destroy panic regression after 3.10.15

> On Fri, 2014-01-17 at 22:49 -0800, Eric Dumazet wrote:
> > On Fri, 2014-01-17 at 17:25 -0800, dormando wrote:
> > > Hi,
> > >
> > > Upgraded a few kernels to the latest 3.10 stable tree while tracking down
> > > a rare kernel panic, seems to have introduced a much more frequent kernel
> > > panic. Takes anywhere from 4 hours to 2 days to trigger:
> > >
> > > <4>[196727.311203] general protection fault: 0000 [#1] SMP
> > > <4>[196727.311224] Modules linked in: xt_TEE xt_dscp xt_DSCP macvlan bridge coretemp crc32_pclmul ghash_clmulni_intel gpio_ich microcode ipmi_watchdog ipmi_devintf sb_edac edac_core lpc_ich mfd_core tpm_tis tpm tpm_bios ipmi_si ipmi_msghandler isci igb libsas i2c_algo_bit ixgbe ptp pps_core mdio
> > > <4>[196727.311333] CPU: 17 PID: 0 Comm: swapper/17 Not tainted 3.10.26 #1
> > > <4>[196727.311344] Hardware name: Supermicro X9DRi-LN4+/X9DR3-LN4+/X9DRi-LN4+/X9DR3-LN4+, BIOS 3.0 07/05/2013
> > > <4>[196727.311364] task: ffff885e6f069700 ti: ffff885e6f072000 task.ti: ffff885e6f072000
> > > <4>[196727.311377] RIP: 0010:[<ffffffff815f8c7f>]  [<ffffffff815f8c7f>] ipv4_dst_destroy+0x4f/0x80
> > > <4>[196727.311399] RSP: 0018:ffff885effd23a70  EFLAGS: 00010282
> > > <4>[196727.311409] RAX: dead000000200200 RBX: ffff8854c398ecc0 RCX: 0000000000000040
> > > <4>[196727.311423] RDX: dead000000100100 RSI: dead000000100100 RDI: dead000000200200
> > > <4>[196727.311437] RBP: ffff885effd23a80 R08: ffffffff815fd9e0 R09: ffff885d5a590800
> > > <4>[196727.311451] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > > <4>[196727.311464] R13: ffffffff81c8c280 R14: 0000000000000000 R15: ffff880e85ee16ce
> > > <4>[196727.311510] FS:  0000000000000000(0000) GS:ffff885effd20000(0000) knlGS:0000000000000000
> > > <4>[196727.311554] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > <4>[196727.311581] CR2: 00007a46751eb000 CR3: 0000005e65688000 CR4: 00000000000407e0
> > > <4>[196727.311625] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > <4>[196727.311669] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > > <4>[196727.311713] Stack:
> > > <4>[196727.311733]  ffff8854c398ecc0 ffff8854c398ecc0 ffff885effd23ab0 ffffffff815b7f42
> > > <4>[196727.311784]  ffff88be6595bc00 ffff8854c398ecc0 0000000000000000 ffff8854c398ecc0
> > > <4>[196727.311834]  ffff885effd23ad0 ffffffff815b86c6 ffff885d5a590800 ffff8816827821c0
> > > <4>[196727.311885] Call Trace:
> > > <4>[196727.311907]  <IRQ>
> > > <4>[196727.311912]  [<ffffffff815b7f42>] dst_destroy+0x32/0xe0
> > > <4>[196727.311959]  [<ffffffff815b86c6>] dst_release+0x56/0x80
> > > <4>[196727.311986]  [<ffffffff81620bd5>] tcp_v4_do_rcv+0x2a5/0x4a0
> > > <4>[196727.312013]  [<ffffffff81622b5a>] tcp_v4_rcv+0x7da/0x820
> > > <4>[196727.312041]  [<ffffffff815fd9e0>] ? ip_rcv_finish+0x360/0x360
> > > <4>[196727.312070]  [<ffffffff815de02d>] ? nf_hook_slow+0x7d/0x150
> > > <4>[196727.312097]  [<ffffffff815fd9e0>] ? ip_rcv_finish+0x360/0x360
> > > <4>[196727.312125]  [<ffffffff815fda92>] ip_local_deliver_finish+0xb2/0x230
> > > <4>[196727.312154]  [<ffffffff815fdd9a>] ip_local_deliver+0x4a/0x90
> > > <4>[196727.312183]  [<ffffffff815fd799>] ip_rcv_finish+0x119/0x360
> > > <4>[196727.312212]  [<ffffffff815fe00b>] ip_rcv+0x22b/0x340
> > > <4>[196727.312242]  [<ffffffffa0339680>] ? macvlan_broadcast+0x160/0x160 [macvlan]
> > > <4>[196727.312275]  [<ffffffff815b0c62>] __netif_receive_skb_core+0x512/0x640
> > > <4>[196727.312308]  [<ffffffff811427fb>] ? kmem_cache_alloc+0x13b/0x150
> > > <4>[196727.312338]  [<ffffffff815b0db1>] __netif_receive_skb+0x21/0x70
> > > <4>[196727.312368]  [<ffffffff815b0fa1>] netif_receive_skb+0x31/0xa0
> > > <4>[196727.312397]  [<ffffffff815b1ae8>] napi_gro_receive+0xe8/0x140
> > > <4>[196727.312433]  [<ffffffffa00274f1>] ixgbe_poll+0x551/0x11f0 [ixgbe]
> > > <4>[196727.312463]  [<ffffffff815fe00b>] ? ip_rcv+0x22b/0x340
> > > <4>[196727.312491]  [<ffffffff815b1691>] net_rx_action+0x111/0x210
> > > <4>[196727.312521]  [<ffffffff815b0db1>] ? __netif_receive_skb+0x21/0x70
> > > <4>[196727.312552]  [<ffffffff810519d0>] __do_softirq+0xd0/0x270
> > > <4>[196727.312583]  [<ffffffff816cef3c>] call_softirq+0x1c/0x30
> > > <4>[196727.312613]  [<ffffffff81004205>] do_softirq+0x55/0x90
> > > <4>[196727.312640]  [<ffffffff81051c85>] irq_exit+0x55/0x60
> > > <4>[196727.312668]  [<ffffffff816cf5c3>] do_IRQ+0x63/0xe0
> > > <4>[196727.312696]  [<ffffffff816c5aaa>] common_interrupt+0x6a/0x6a
> > > <4>[196727.312722]  <EOI>
> > > <4>[196727.312727]  [<ffffffff8100a150>] ? default_idle+0x20/0xe0
> > > <4>[196727.312775]  [<ffffffff8100a8ff>] arch_cpu_idle+0xf/0x20
> > > <4>[196727.312803]  [<ffffffff8108d330>] cpu_startup_entry+0xc0/0x270
> > > <4>[196727.312833]  [<ffffffff816b276e>] start_secondary+0x1f9/0x200
> > > <4>[196727.312860] Code: 4a 9f e9 81 e8 13 cb 0c 00 48 8b 93 b0 00 00 00 48 bf 00 02 20 00 00 00 ad de 48 8b 83 b8 00 00 00 48 be 00 01 10 00 00 00 ad de <48> 89 42 08 48 89 10 48 89 bb b8 00 00 00 48 c7 c7 4a 9f e9 81
> > > <1>[196727.313071] RIP  [<ffffffff815f8c7f>] ipv4_dst_destroy+0x4f/0x80
> > > <4>[196727.313100]  RSP <ffff885effd23a70>
> > > <4>[196727.313377] ---[ end trace 64b3f14fae0f2e29 ]---
> > > <0>[196727.380908] Kernel panic - not syncing: Fatal exception in interrupt
> > >
> > >
> > > ... bisecting it's going to be a pain... I tried eyeballing the diffs and
> > > am trying a revert or two.
> > >
> > > We've hit it in .25, .26 so far. I have .27 running but not sure if it
> > > crashed, so the change exists between .15 and .25.
> >
> > Please try following fix, thanks for the report !
> >
> > diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> > index 25071b48921c..78a50a22298a 100644
> > --- a/net/ipv4/route.c
> > +++ b/net/ipv4/route.c
> > @@ -1333,7 +1333,7 @@ static void ipv4_dst_destroy(struct dst_entry
> > *dst)
> >
> >  	if (!list_empty(&rt->rt_uncached)) {
> >  		spin_lock_bh(&rt_uncached_lock);
> > -		list_del(&rt->rt_uncached);
> > +		list_del_init(&rt->rt_uncached);
> >  		spin_unlock_bh(&rt_uncached_lock);
> >  	}
> >  }
> >
>
> Problem could come from this commit, in linux 3.10.23,
> you also could try to revert it
>
> commit 62713c4b6bc10c2d082ee1540e11b01a2b2162ab
> Author: Alexei Starovoitov <ast@...mgrid.com>
> Date:   Tue Nov 19 19:12:34 2013 -0800
>
>     ipv4: fix race in concurrent ip_route_input_slow()
>
>     [ Upstream commit dcdfdf56b4a6c9437fc37dbc9cee94a788f9b0c4 ]
>
>     CPUs can ask for local route via ip_route_input_noref() concurrently.
>     if nh_rth_input is not cached yet, CPUs will proceed to allocate
>     equivalent DSTs on 'lo' and then will try to cache them in nh_rth_input
>     via rt_cache_route()
>     Most of the time they succeed, but on occasion the following two lines:
>         orig = *p;
>         prev = cmpxchg(p, orig, rt);
>     in rt_cache_route() do race and one of the cpus fails to complete cmpxchg.
>     But ip_route_input_slow() doesn't check the return code of rt_cache_route(),
>     so dst is leaking. dst_destroy() is never called and 'lo' device
>     refcnt doesn't go to zero, which can be seen in the logs as:
>         unregister_netdevice: waiting for lo to become free. Usage count = 1
>     Adding mdelay() between above two lines makes it easily reproducible.
>     Fix it similar to nh_pcpu_rth_output case.
>
>     Fixes: d2d68ba9fe8b ("ipv4: Cache input routes in fib_info nexthops.")
>     Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
>     Signed-off-by: David S. Miller <davem@...emloft.net>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>

Heh. I spent an hour squinting at the difflog from .15 to .25 and this was
my best guess. I have a kernel running in production with only this
reverted as of ~5 hours ago. Won't know if it helps for a day or two.

I'm building a kernel now with your route patch, but 62713c4 *not*
reverted, which I can throw on a different machine. Does this sound like a
good idea?

Thanks for your quick help as always!
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