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HTML Code: [ 262.740000] Unable to handle kernel NULL pointer dereference at virtual address 000000d0 [ 262.740000] pgd = c0004000 [ 262.740000] [000000d0] *pgd=00000000 [ 262.740000] Internal error: Oops: 17 ...
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  1. #1
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    Kernel Oops at tty_buffer_request_room when using pppd program


    HTML Code:
    [  262.740000] Unable to handle kernel NULL pointer dereference at virtual address 000000d0
    [  262.740000] pgd = c0004000
    [  262.740000] [000000d0] *pgd=00000000
    [  262.740000] Internal error: Oops: 17 [#1] PREEMPT
    [  262.740000] Modules linked in: option usb_wwan usbserial ehci_hcd imx_iocontrol [last unloaded: imx_dtrrts]
    [  262.740000] CPU: 0    Not tainted  (2.6.31-207-g7286c01 #2)
    [  262.740000] PC is at tty_buffer_request_room+0x2c/0x150
    [  262.740000] LR is at tty_insert_flip_string_fixed_flag+0x2c/0x8c
    [  262.740000] pc : [<c016be58>]    lr : [<c016c0e4>]    psr: 80000093
    [  262.740000] sp : c03bfde8  ip : c0410480  fp : ffffff8d
    [  262.740000] r10: 0000001f  r9 : 80000093  r8 : 0000001f
    [  262.740000] r7 : 00000000  r6 : d59a1000  r5 : 00000000  r4 : d5a11d60
    [  262.740000] r3 : 00010003  r2 : c03be000  r1 : 0000001f  r0 : 00000000
    [  262.740000] Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
    [  262.740000] Control: 0005317f  Table: 970b0000  DAC: 00000017
    [  262.740000] Process swapper (pid: 0, stack limit = 0xc03be270)
    [  262.740000] Stack: (0xc03bfde8 to 0xc03c0000)
    [  262.740000] fde0:                   d5a11d60 00000000 d59a1000 00000000 0000001f 00000000 
    [  262.740000] fe00: 00000000 c016c0e4 d5a11d60 00000000 bf043394 00000000 d59a1000 00000000 
    [  262.740000] fe20: d58f3000 bf0405b0 c03c6d80 00000000 c03c6da0 d5a11d60 00000000 d5a11d60 
    [  262.740000] fe40: d7216e00 d5a11ce0 d7216ec8 c01d0af0 d782c360 c03be000 00000000 bf00ef3c 
    [  262.740000] fe60: 00000000 fde682a0 ffffff8d fde67180 fde68180 bf00f990 00000106 fde671cc 
    [  262.740000] fe80: fde68060 fde680f8 00000000 00000001 c03bfec8 fde67180 60000013 00000000 
    [  262.740000] fea0: d7216ec8 00000023 00000000 d7216e00 00000000 bf00fdac 0fada137 00000109 
    [  262.740000] fec0: 00000001 00000000 2c33fd4a 00000106 2de54480 00000106 c03c8b08 00000106 
    [  262.740000] fee0: c03c90a8 00000000 60000013 d7216ec8 000ce089 00000023 00000000 d7216e00 
    [  262.740000] ff00: 00000000 bf014324 0000b29c d7216e00 60000013 00000002 c03be000 00000023 
    [  262.740000] ff20: 00000000 c01d0f00 c03be000 d7bf4420 d7bf4420 c006fa3c c03be000 c03c9d34 
    [  262.740000] ff40: d7bf4420 00000023 00000001 c03be000 8001f7c0 c0071ea0 c03be000 00000023 
    [  262.740000] ff60: 00000000 00230000 00000002 c002406c 00000002 0000001f fc400000 c0024a0c 
    [  262.740000] ff80: 00000000 0005317f 0005217f 80000013 c03be000 c03e7af0 c0020ca0 c03c1b80 
    [  262.740000] ffa0: 8001f7f4 41069264 8001f7c0 00000000 800000d3 c03bffc8 c0025e54 c0025e60 
    [  262.740000] ffc0: 80000013 ffffffff 00000000 c0025d90 c04202cc c000899c c0008354 00000000 
    [  262.740000] ffe0: 00000000 c0020ca0 00053175 c03e7d78 c00210a4 80008034 00000000 00000000 
    [  262.740000] [<c016be58>] (tty_buffer_request_room+0x2c/0x150) from [<c016c0e4>] (tty_insert_flip_string_fixed_flag+0x2c/0x8c)
    [  262.740000] [<c016c0e4>] (tty_insert_flip_string_fixed_flag+0x2c/0x8c) from [<bf0405b0>] (usb_wwan_indat_callback+0x9c/0x138 [usb_wwan])
    [  262.740000] [<bf0405b0>] (usb_wwan_indat_callback+0x9c/0x138 [usb_wwan]) from [<c01d0af0>] (usb_hcd_giveback_urb+0x78/0xc8)
    [  262.740000] [<c01d0af0>] (usb_hcd_giveback_urb+0x78/0xc8) from [<bf00ef3c>] (ehci_urb_done+0xac/0xc0 [ehci_hcd])
    [  262.740000] [<bf00ef3c>] (ehci_urb_done+0xac/0xc0 [ehci_hcd]) from [<bf00f990>] (qh_completions+0xb4/0x400 [ehci_hcd])
    [  262.740000] [<bf00f990>] (qh_completions+0xb4/0x400 [ehci_hcd]) from [<bf00fdac>] (ehci_work+0xd0/0x870 [ehci_hcd])
    [  262.740000] [<bf00fdac>] (ehci_work+0xd0/0x870 [ehci_hcd]) from [<bf014324>] (ehci_irq+0x1b8/0x200 [ehci_hcd])
    [  262.740000] [<bf014324>] (ehci_irq+0x1b8/0x200 [ehci_hcd]) from [<c01d0f00>] (usb_hcd_irq+0xa4/0x100)
    [  262.740000] [<c01d0f00>] (usb_hcd_irq+0xa4/0x100) from [<c006fa3c>] (handle_IRQ_event+0xa4/0x1e0)
    [  262.740000] [<c006fa3c>] (handle_IRQ_event+0xa4/0x1e0) from [<c0071ea0>] (handle_level_irq+0xc8/0x158)
    [  262.740000] [<c0071ea0>] (handle_level_irq+0xc8/0x158) from [<c002406c>] (_text+0x6c/0x8c)
    [  262.740000] [<c002406c>] (_text+0x6c/0x8c) from [<c0024a0c>] (__irq_svc+0x4c/0x98)
    [  262.740000] Exception stack(0xc03bff80 to 0xc03bffc8)
    [  262.740000] ff80: 00000000 0005317f 0005217f 80000013 c03be000 c03e7af0 c0020ca0 c03c1b80 
    [  262.740000] ffa0: 8001f7f4 41069264 8001f7c0 00000000 800000d3 c03bffc8 c0025e54 c0025e60 
    [  262.740000] ffc0: 80000013 ffffffff                                                       
    [  262.740000] [<c0024a0c>] (__irq_svc+0x4c/0x98) from [<c0025e60>] (default_idle+0x2c/0x34)
    [  262.740000] [<c0025e60>] (default_idle+0x2c/0x34) from [<c0025d90>] (cpu_idle+0x5c/0xbc)
    [  262.740000] [<c0025d90>] (cpu_idle+0x5c/0xbc) from [<c000899c>] (start_kernel+0x234/0x290)
    [  262.740000] [<c000899c>] (start_kernel+0x234/0x290) from [<80008034>] (0x80008034)
    [  262.740000] Code: e3c2203f e5923004 e2833001 e5823004 (e59060d0) 
    [  262.740000] Kernel panic - not syncing: Fatal exception in interrupt
    please tell me what is the problem here. it is related with buffer alloation ?

    thanks in advance

  2. #2
    Linux Guru Rubberman's Avatar
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    Is there a kernel module or modification that you did, or installed? Or is this a standard kernel and ppp module that you installed from the OS distribution package manager (or was part of the original distribution)? Also, what distribution+version+kernel are you running?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
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    I am using 2.6.31 kernel in which there is no usb_wwan.c . took it from 2.6.35 kernel and did some modifications in 2.6.31 kernel (like in tty_buffer.c tty.h ... and some files).
    with this my USB modem is working up to some time then after that getting kernel panic as i said in previous post.

  4. #4
    Linux Guru Rubberman's Avatar
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    Ok. Between 2.6.31 and 2.6.35 I believe (from what I remember at least) there were some significant kernel structural changes. This may be the cause of your problems.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  5. #5
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    yes , exactly i did some of the changes(additions) in structure elements.

    i went through the function tty_buffer_request_room in tty_buffer.c seems to be similar in both 2.6.31 and 2.6.35.

    Give me some idea on what below snap indicates.

    HTML Code:
    [ 3713.020000] CPU: 0    Not tainted  (2.6.31-207-g7286c01 #2)
    [ 3713.020000] PC is at tty_buffer_request_room+0x2c/0x150
    [ 3713.020000] LR is at tty_insert_flip_string_fixed_flag+0x2c/0x8c
    [ 3713.020000] pc : [<c016be58>]    lr : [<c016c0e4>]    psr: 80000093
    [ 3713.020000] sp : c03bfde8  ip : c0410480  fp : ffffff8d
    [ 3713.020000] r10: 0000001f  r9 : 80000093  r8 : 0000001f
    [ 3713.020000] r7 : 00000000  r6 : d5907000  r5 : 00000000  r4 : d72db160
    [ 3713.020000] r3 : 00010003  r2 : c03be000  r1 : 0000001f  r0 : 00000000
    [ 3713.020000] Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel

  6. #6
    Linux Guru Rubberman's Avatar
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    Not sure what LR is, but pretty sure PC/pc is the program counter (where it is executing - inside tty_buffer_request_room). sp, ip, and fp are various pointers. And the rN values are the CPU registers. Is this an ARM processor?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  7. #7
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    Yes it is ARM processor
    here LR is link register.

    according to you is problem inside tty_buffer_request_room ?

  8. #8
    Linux Guru Rubberman's Avatar
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    Well, I am at the limits of my kernel coding capabilities! Sorry, but I'll have to defer to more expert folk...
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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