Subject: CPSW bug with AM437x SK

From: Felipe Balbi <[email-masked]>
Date: Thu, 2 Oct 2014 20:04:18 -0500

Hi Mugunthan,

I noticed that *really* rarely I get the skb panic below. What I have
here is an AM437x SK running v3.17-rc6, with NFS root. Once booted, then
I run cyclictest and hackbench (this one in an infinite loop) an
eventually this will trigger.

File system is mounted as read-only and another board (BBB) is also
mounting the exact same NFS root also as read-only.

It takes a while to reproduce but it is the second time I managed to
reproduce with the exact same setup. .config attached.

[  260.881326] skbuff: skb_over_panic: text:c0605aac len:100 put:100 head:  (null) data:  (null) tail:0x64 end:0x0 dev:-
[  260.892732] ------------[ cut here ]------------
[  260.897590] kernel BUG at net/core/skbuff.c:100!
[  260.902441] Internal error: Oops - BUG: 0 [#1] SMP ARM
[  260.907820] Modules linked in: xhci_hcd snd_soc_davinci_mcasp snd_soc_edma snd_soc_omap snd_soc_evm snd_soc_tlv320aic3x snd_soc_core dwc3 snd_compress omapdrm snd_pcm_dmaengine snd_pcm snd_timer snd fb_sys_fops lis3lv02d_i2c panel_dpi matrix_keypad lis3lv02d dwc3_omap input_polldev soundcore
[  260.935072] CPU: 0 PID: 8997 Comm: hackbench Not tainted 3.17.0-rc6-00456-gd8da063-dirty #223
[  260.944015] task: ead16d80 ti: ec084000 task.ti: ec084000
[  260.949693] PC is at skb_panic+0x64/0x70
[  260.953824] LR is at vprintk_emit+0x258/0x5e0
[  260.958386] pc : [<c0648d48>]    lr : [<c009459c>]    psr: 600f0013
[  260.958386] sp : ec085db8  ip : ec085d20  fp : ec085dec
[  260.970435] r10: 00000000  r9 : e8881ac0  r8 : 00000001
[  260.975909] r7 : c087e79c  r6 : 00000000  r5 : 00000064  r4 : 00000000
[  260.982747] r3 : ead16d80  r2 : 00000000  r1 : edfb5544  r0 : 0000006a
[  260.989599] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[  260.997090] Control: 10c5387d  Table: a91c0059  DAC: 00000015
[  261.003116] Process hackbench (pid: 8997, stack limit = 0xec084248)
[  261.009674] Stack: (0xec085db8 to 0xec086000)
[  261.014233] 5da0:                                                       00000064 00000000
[  261.022817] 5dc0: 00000000 00000064 00000000 ea9ed240 00000064 00000064 00000000 00000000
[  261.031393] 5de0: ec085e0c ec085df0 c0565edc c0648cf0 00000064 e8881cac e893e1c0 00000000
[  261.039955] 5e00: ec085e7c ec085e10 c0605aac c0565e8c ec085e38 00000003 c064e674 e893e254
[  261.048537] 5e20: ec085e80 ec085ea0 e893e4d4 00000001 00000064 ece0e840 00000000 00000000
[  261.057108] 5e40: 00000000 00000000 ffffffff ffffffff c00899e0 ece0e840 e893f940 00000064
[  261.065686] 5e60: 00000064 00000064 bed59b48 00000000 ec085edc ec085e80 c055b364 c0605954
[  261.074259] 5e80: 00000000 c018b704 ec085ee4 00000064 ece0e840 c0089d60 ec085e3c ec085ea0
[  261.082843] 5ea0: 00000000 00000000 ec085ee8 00000001 00000000 00000000 00000000 ec085ef0
[  261.091397] 5ec0: 00000000 00000000 00000000 ec085f78 ec085f44 ec085ee0 c014c42c c055b294
[  261.099953] 5ee0: 00000000 00000000 bed59b48 00000064 e893f940 00000000 00000000 ec085e80
[  261.108502] 5f00: ead16d80 00000000 00000000 00000000 00000000 00000000 00000064 00000000
[  261.117089] 5f20: 00000000 00000000 e893f940 e893f940 bed59b48 ec085f78 ec085f74 ec085f48
[  261.125662] 5f40: c014cf70 c014c3ac 00000001 c016a9d8 00000000 00000000 e893f940 e893f940
[  261.134242] 5f60: 00000064 bed59b48 ec085fa4 ec085f78 c014d564 c014ce64 00000000 00000000
[  261.142843] 5f80: 00000064 00024c6c bed59b48 00000004 c000efc4 ec084000 00000000 ec085fa8
[  261.151417] 5fa0: c000ed40 c014d524 00000064 00024c6c 0000000c bed59b48 00000064 00000014
[  261.159992] 5fc0: 00000064 00024c6c bed59b48 00000004 00000004 00024c50 000221ac 00000000
[  261.168555] 5fe0: 00000000 bed59b44 000113a1 b6f204d6 600f0030 0000000c 00000000 00000000
[  261.177168] [<c0648d48>] (skb_panic) from [<c0565edc>] (skb_put+0x5c/0x60)
[  261.184415] [<c0565edc>] (skb_put) from [<c0605aac>] (unix_stream_sendmsg+0x164/0x390)
[  261.192712] [<c0605aac>] (unix_stream_sendmsg) from [<c055b364>] (sock_aio_write+0xdc/0xfc)
[  261.201475] [<c055b364>] (sock_aio_write) from [<c014c42c>] (do_sync_write+0x8c/0xb4)
[  261.209697] [<c014c42c>] (do_sync_write) from [<c014cf70>] (vfs_write+0x118/0x1c0)
[  261.217652] [<c014cf70>] (vfs_write) from [<c014d564>] (SyS_write+0x4c/0xa0)
[  261.225054] [<c014d564>] (SyS_write) from [<c000ed40>] (ret_fast_syscall+0x0/0x48)
[  261.232988] Code: e58d4008 e58de00c e59f0008 ebfff48e (e7f001f2) 
[  261.239378] ---[ end trace d64258d586f40104 ]---

-- 
balbi