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    SubjectRe: 2.6.24-rc4-mm1 kobject changes broken with hvcs driver on powerpc
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    On Thu, 2007-12-06 at 12:31 -0800, Greg KH wrote:
    > On Fri, Dec 07, 2007 at 12:28:58AM +0530, Balbir Singh wrote:
    > > Greg KH wrote:
    > >
    > > >> Why release the spinlock here? It's done after the count is incremented.
    > > >> This patch does not seem correct.
    > > >
    > > > Doh, you are correct, I'll make sure that I fix this up before applying
    > > > it.
    > > >
    > > > thanks,
    > > >
    > > > greg k-h
    > >
    > > Hi, Greg,
    > >
    > > I ran some tests with the fixed up version of this patch and the system
    > > fails to come up.
    > >
    > > I see the WARN_ON in lib/kref.c:33 and the system fails to boot beyond
    > > that point. I have not yet found time to debug it though.
    >
    > That's not good, that warning means that someone has tried to use this
    > kref _before_ it was initialized, so there is a logic error in the code
    > that was previously being papered over with the lack of this message in
    > the kobject code.
    >
    > I do have this same message availble as a patch for the kobject core, it
    > would be interesting if you could just run 2.6.24-rc4 with just this
    > patch:
    > http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/gregkh-01-driver/kobject-warn.patch
    >
    > it might take some fuzz to fit properly, but all you really want to do
    > is add:
    > WARN_ON(atomic_read(&kobj->kref.refcount));
    > before the kref_init() call in kobject_init().
    >
    > thanks,
    >
    > greg k-h

    2.6.24-rc4 with above patch booted fine without any warnings.
    But 2.6.24-rc4-mm1 doesn't boot, it hangs after following messages.


    e100: Intel(R) PRO/100 Network Driver, 3.5.23-k4-NAPI
    e100: Copyright(c) 1999-2006 Intel Corporation
    ipr: IBM Power RAID SCSI Device Driver version: 2.4.1 (April 24, 2007)
    ipr 0000:d0:01.0: Found IOA with IRQ: 119
    ipr 0000:d0:01.0: Starting IOA initialization sequence.
    ipr 0000:d0:01.0: Adapter firmware version: 020A005E
    ipr 0000:d0:01.0: IOA initialized.
    scsi0 : IBM 570B Storage Adapter
    scsi 0:0:3:0: Direct-Access IBM H0 HUS103014FL3800 RPQF PQ: 0 ANSI: 4
    scsi 0:0:5:0: Direct-Access IBM H0 HUS103014FL3800 RPQF PQ: 0 ANSI: 4
    scsi 0:0:8:0: Direct-Access IBM H0 HUS103014FL3800 RPQF PQ: 0 ANSI: 4
    scsi 0:0:15:0: Enclosure IBM VSBPD4E2 U4SCSI 7134 PQ: 0 ANSI: 2
    ------------[ cut here ]------------
    Badness at lib/kref.c:33
    NIP: c0000000002e1254 LR: c0000000002dfbd8 CTR: c0000000002e60f0
    REGS: c00000003f0db050 TRAP: 0700 Not tainted (2.6.24-rc4-mm1)
    MSR: 8000000000029032 <EE,ME,IR,DR> CR: 28002042 XER: 0000000f
    TASK = c00000003f0d78d0[1] 'swapper' THREAD: c00000003f0d8000 CPU: 0
    GPR00: 0000000000000000 c00000003f0db2d0 c000000000724098 c00000003f131620
    GPR04: fffffffffffffff1 fffffffffffffffe 000000000000000a ffffffffffffffff
    GPR08: c00000003d4d9000 c00000003f0cbfe0 c000000000556591 0000000000000073
    GPR12: 0000000024002084 c000000000651980 0000000000000000 0000000000000000
    GPR16: 0000000000000000 d000080080080000 c00000000064d6f0 c00000003d4d9570
    GPR20: c00000003d4d94b8 0000000000000002 c00000003d4d9170 c00000003d4d9170
    GPR24: c00000003d4d9000 0000000000000001 c00000003d570d58 c00000003d570d18
    GPR28: 0000000000000000 c00000003d4d9260 c0000000006b5400 c00000003f131618
    NIP [c0000000002e1254] .kref_get+0x10/0x2c
    LR [c0000000002dfbd8] .kobject_get+0x24/0x40
    Call Trace:
    [c00000003f0db2d0] [c00000003f0db360] 0xc00000003f0db360 (unreliable)
    [c00000003f0db350] [c0000000002e00e8] .kobject_add+0x8c/0x21c
    [c00000003f0db3e0] [c000000000344b00] .device_add+0xd4/0x680
    [c00000003f0db4a0] [c0000000003a1c4c] .scsi_alloc_target+0x218/0x404
    [c00000003f0db570] [c0000000003a1fb4] .__scsi_scan_target+0xa8/0x640
    [c00000003f0db6b0] [c0000000003a25c4] .scsi_scan_channel+0x78/0xdc
    [c00000003f0db750] [c0000000003a26f8] .scsi_scan_host_selected+0xd0/0x140
    [c00000003f0db7f0] [c0000000003c3ff4] .ipr_probe+0x1270/0x1348
    [c00000003f0db960] [c0000000002f4808] .pci_device_probe+0x124/0x194
    [c00000003f0dba10] [c000000000347e8c] .driver_probe_device+0x110/0x1f0
    [c00000003f0dbaa0] [c000000000348014] .__driver_attach+0xa8/0x134
    [c00000003f0dbb30] [c0000000003472ac] .bus_for_each_dev+0x80/0xd0
    [c00000003f0dbbe0] [c000000000347c14] .driver_attach+0x28/0x40
    [c00000003f0dbc60] [c000000000346788] .bus_add_driver+0xfc/0x2d0
    [c00000003f0dbd10] [c0000000003482cc] .driver_register+0x80/0x9c
    [c00000003f0dbd90] [c0000000002f4bb0] .__pci_register_driver+0x5c/0xcc
    [c00000003f0dbe20] [c000000000604b38] .ipr_init+0x38/0x50
    [c00000003f0dbea0] [c0000000005d6428] .kernel_init+0x214/0x3ec
    [c00000003f0dbf90] [c000000000026734] .kernel_thread+0x4c/0x68
    Instruction dump:
    e8410028 39200001 38210080 7d234b78 e8010010 ebc1fff0 7c0803a6 4e800020
    80030000 7c0007b4 2f800000 409e0008 <0fe00000> 7c001828 30000001


    Thanks,
    Badari



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