[linux-dvb] Kernel module crash (divide error)

Rutger ter Borg rutger at terborg.net
Sun Nov 18 11:09:48 CET 2007

Dear Linux DVB developers,

I've been trying to get DVB-C working on my system, meanwhile with multiple 
DVB-C cards (KNC1 and Technotrend budget cards), with their CI counterparts, 
and Alphacrypt CAM, so far unfortunately without success. In my 
trial-and-error path I've encountered a possible bug in the linuxtv 
dvb-drivers. Apparently, it's possible to get accepted by the kernel a symbol 
rate of zero, causing a divide by zero error. 

This is valid for (Debian) kernels 2.6.18-4, 2.6.22-3, and 2.6.23-1. 

$ dvbstream -f 388000000 -s 0 -o > test.mpg
dvbstream v0.6 - (C) Dave Chapman 2001-2004
Released under the GPL.
Latest version available from http://www.linuxstb.org/
Tuning to 37200 Hz
Using DVB card "ST STV0297 DVB-C", freq=37200
tuning DVB-C to 37200000, srate=0
Getting frontend status

Message from syslogd at fraggle at Sun Nov 18 10:55:53 2007 ...
fraggle kernel: divide error: 0000 [1] SMP

kernel messages:
kernel: Pid: 3675, comm: kdvb-fe-0 Not tainted 2.6.18-4-amd64 #1
kernel: RIP: 0010:[<ffffffff88154abc>]  
[<ffffffff88154abc>] :stv0297:stv0297_set_frontend+0x4b0/0x834
kernel: RSP: 0018:ffff810034999e30  EFLAGS: 00010297
kernel: RAX: fffffffff0600000 RBX: 0000000000000000 RCX: fffffffff0600000
kernel: RDX: ffffffffffffffff RSI: 0000000000000000 RDI: ffff81003e962c00
kernel: RBP: ffff81003e962c00 R08: 0000000000000002 R09: 0000000000000003
kernel: R10: 0000000000000001 R11: 0000000000000001 R12: 00000000000003e8
kernel: R13: 0000000000000009 R14: ffff81003e961008 R15: 0000000000000001
kernel: FS:  00002af0b4a3c6e0(0000) GS:ffffffff80521000(0000) 
kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
kernel: CR2: 00002af0b47afb80 CR3: 000000003843a000 CR4: 00000000000006e0
kernel: Process kdvb-fe-0 (pid: 3675, threadinfo ffff810034998000, task 
kernel: Stack:  ffff810034999e90 00000064ffffffff 0000014afffffc18 
kernel:  ffff81003e962c10 0000000000000001 0000000000000002 000000000237a080
kernel:  ffff810039ed0880 ffffffff8816f8c1 ffff81003e961000 ffff81003e962c10
kernel: Call Trace:
[<ffffffff8816f8c1>] :dvb_core:dvb_frontend_swzigzag_autotune+0x18c/0x1b4
kernel:  [<ffffffff881700ef>] :dvb_core:dvb_frontend_swzigzag+0x1b8/0x21c
kernel:  [<ffffffff8024b225>] finish_wait+0x32/0x5d
kernel:  [<ffffffff88170cf6>] :dvb_core:dvb_frontend_thread+0x297/0x31b
kernel:  [<ffffffff80290381>] autoremove_wake_function+0x0/0x2e
kernel:  [<ffffffff80259360>] child_rip+0xa/0x12
kernel:  [<ffffffff8022a91a>] dummy_inode_permission+0x0/0x3
kernel:  [<ffffffff88170a5f>] :dvb_core:dvb_frontend_thread+0x0/0x31b
kernel:  [<ffffffff80259356>] child_rip+0x0/0x12
kernel: Code: 48 f7 fe ba 40 42 0f 00 be 60 00 00 00 48 89 c1 48 c1 e1 0a
kernel:  RSP <ffff810034999e30>

Kind regards,

Rutger ter Borg

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