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    SubjectRe: [git pull] DVB + ieee1394: firedtv driver

    On Thu, 26 Feb 2009, Stefan Richter wrote:
    > Alas I have no Linux box at hand before Saturday. I wonder, was
    > ieee1394_bus_type not yet registered (i.e. ieee1394's ieee1394_init() not yet
    > called) at the moment when fdtv_init is executed?
    > Or what else could have been the NULL pointer dereference in driver_find?

    Afaik, the only way that NULL pointer dereference can happen is if

    struct kobject *k = kset_find_obj(bus->p->drivers_kset, name);

    gets a NULL pointer exception either because of a NULL "bus" pointer as
    the argument, or if "bus->p" is NULL.

    And in this case, it's the latter. The Code: decode shows the whole
    function in this case:

    1c: 55 push %rbp
    1d: 89 e5 mov %esp,%ebp
    1f: e8 34 5f c8 ff callq 0xffffffffffc85f58
    24: 89 c1 mov %eax,%ecx
    26: 8b 42 38 mov 0x38(%rdx),%eax
    29: 89 ca mov %ecx,%edx
    2b:* 8b 40 54 mov 0x54(%rax),%eax <-- trapping instruction
    2e: e8 6c 48 f9 ff callq 0xfffffffffff9489f
    33: 31 d2 xor %edx,%edx
    35: 85 c0 test %eax,%eax
    37: 74 03 je 0x3c
    39: 8b 50 6c mov 0x6c(%rax),%edx
    3c: 5d pop %rbp
    3d: 89 d0 mov %edx,%eax
    3f: c3 retq

    and that first "callq" seems to be due to Ingo having function tracing on,
    while the second callq would have been that 'kset_find_obj()' thing.

    So it does look like "&ieee1394_bus_type" has simply not been initialized
    yet. It looks like ieee1394_init() is called too late.

    Two choices that I can see:

    - do the ieee1394_init() as a fs_initcall(), earlier

    - move drivers/ieee1394 linking up to before drivers/media

    but I suspect that drivers/media wants to be early, in order to do the
    _media_ layer initialization early.

    Does this work?


    drivers/ieee1394/ieee1394_core.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/drivers/ieee1394/ieee1394_core.c b/drivers/ieee1394/ieee1394_core.c
    index 1028e72..8723380 100644
    --- a/drivers/ieee1394/ieee1394_core.c
    +++ b/drivers/ieee1394/ieee1394_core.c
    @@ -1275,7 +1275,7 @@ static void __exit ieee1394_cleanup(void)
    unregister_chrdev_region(IEEE1394_CORE_DEV, 256);


    /* Exported symbols */

     \ /
      Last update: 2009-02-26 17:43    [W:0.022 / U:8.232 seconds]
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