[ltt-dev] kernel Oops in ltt_buffer_begin_callback / ltt_create_buf_file_callback

[Andrew McDermott]

[ Sorry for the duplicate; was using the old mail alias. ]

I am using:

  linux-2.6.27-lttng-0.43
  ltt-control-0.55-16102008

and tried to create a trace with:

  /usr/local/ltt-control-0.55/bin/lttctl -x 32768 -n trace4 -d -l /mnt/debugfs/ltt -t /tmp/trace4

but that gave me a SEGV followed by the following Oops:

    [82616.737763] Creating trace trace4
    [82616.740990] BUG: unable to handle kernel NULL pointer dereference at 00000008
    [82616.740996] IP: [<c033aa9a>] ltt_buffer_begin_callback+0x3a/0x16c
    [82616.741014] *pde = 00000000 
    [82616.741019] Oops: 0000 [#1] SMP 
    [82616.741023] LTT NESTING LEVEL : 0
    [82616.741026] Modules linked in: ltt_control ltt_statedump
    [82616.741032] 
    [82616.741035] Pid: 8561, comm: lttctl Not tainted (2.6.27-lttng-0.43 #5)
    [82616.741039] EIP: 0060:[<c033aa9a>] EFLAGS: 00010246 CPU: 0
    [82616.741043] EIP is at ltt_buffer_begin_callback+0x3a/0x16c
    [82616.741046] EAX: 00000000 EBX: f7060e00 ECX: efe62000 EDX: 00100000
    [82616.741049] ESI: 00000000 EDI: 00000000 EBP: eee93bf8 ESP: eee93bd8
    [82616.741052]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
    [82616.741056] Process lttctl (pid: 8561, ti=eee92000 task=eecd3160 task.ti=eee92000)
    [82616.741058] Stack: dd4759f8 0000eff5 f7060e00 efe62000 00000000 efdca700 fffffff4 ec6e9600 
    [82616.741067]        eee93c24 c033af5a 00000000 00000100 e907f880 effe4c00 efe62000 00008000 
    [82616.741076]        ec6e9654 f7060e00 ec74a800 eee93c50 c033b869 f7060e00 f7060e00 effe4c00 
    [82616.741084] Call Trace:
    [82616.741087]  [<c033af5a>] ? ltt_create_buf_file_callback+0xd0/0x11c
    [82616.741094]  [<c033b869>] ? relay_open_buf+0x165/0x1d7
    [82616.741099]  [<c033ba85>] ? ltt_relay_open+0xf6/0x18d
    [82616.741104]  [<c033a690>] ? ltt_relay_create_channel+0x11d/0x18c
    [82616.741109]  [<c0339b48>] ? ltt_control+0x60a/0x77c
    [82616.741114]  [<c03144b1>] ? selinux_netlink_recv+0x4d/0x57
    [82616.741120]  [<f885f159>] ? ltt_control_input+0xfd/0x19c [ltt_control]
    [82616.741129]  [<c04f2421>] ? netlink_unicast+0x1a2/0x203
    [82616.741137]  [<c04f2b05>] ? netlink_sendmsg+0x241/0x24e
    [82616.741142]  [<c04d4a6e>] ? sock_sendmsg+0xe9/0x138
    [82616.741149]  [<c02319a5>] ? autoremove_wake_function+0x0/0x30
    [82616.741154]  [<c03e5cfd>] ? tg3_poll+0x807/0x8b1
    [82616.741160]  [<c025aeb9>] ? find_get_page+0x1d/0x78
    [82616.741166]  [<c04d5389>] ? sys_sendto+0xa4/0xc3
    [82616.741171]  [<c025b089>] ? unlock_page+0x25/0x28
    [82616.741175]  [<c0266710>] ? __do_fault+0x2a9/0x2e3
    [82616.741181]  [<c030f197>] ? security_d_instantiate+0x1c/0x1e
    [82616.741188]  [<c0267968>] ? handle_mm_fault+0x2b3/0x5ee
    [82616.741193]  [<c04d5b61>] ? sys_socketcall+0x12c/0x1ca
    [82616.741198]  [<c0203942>] ? syscall_call+0x7/0xb
    [82616.741203]  [<c05b0000>] ? rtl8169_init_one+0x435/0xab4
    [82616.741209]  =======================
    [82616.741211] Code: 8b 5d e8 89 55 e0 89 4d e4 8b 00 8b 48 18 89 4d ec 8b 50 04 8b 40 0c 0f af fa 48 21 c7 31 c0 85 d7 0f 95 c0 89 45 f0 8b 74 83 54 <8b> 46 08 39 c7 72 09 05 00 10 00 00 39 c7 72 0d 8b 45 e8 8b 55 
    [82616.741259] EIP: [<c033aa9a>] ltt_buffer_begin_callback+0x3a/0x16c SS:ESP 0068:eee93bd8
    [82616.741266] ---[ end trace 2fce5939568266d6 ]---

HTH,
Andy.