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    SubjectRe: in 2.6.23-rc3-git7 in do_cciss_intr
    Miller, Mike (OS Dev) wrote:
    >
    >> -----Original Message-----
    >> From: Jens Axboe [mailto:jens.axboe@oracle.com]
    >> Sent: Wednesday, November 19, 2008 2:52 AM
    >> To: Randy Dunlap
    >> Cc: scsi; Miller, Mike (OS Dev); James Bottomley; lkml; akpm
    >> Subject: Re: in 2.6.23-rc3-git7 in do_cciss_intr
    >>
    >> On Tue, Nov 18 2008, Randy Dunlap wrote:
    >>> Randy Dunlap wrote:
    >>>> Randy Dunlap wrote:
    >>>>> Miller, Mike (OS Dev) wrote:
    >>>>>>> -----Original Message-----
    >>>>>>> From: Randy Dunlap [mailto:randy.dunlap@oracle.com]
    >>>>>>> Sent: Thursday, September 25, 2008 3:40 PM
    >>>>>>> To: scsi
    >>>>>>> Cc: Jens Axboe; Miller, Mike (OS Dev); James Bottomley; lkml;
    >>>>>>> akpm
    >>>>>>> Subject: Re: in 2.6.23-rc3-git7 in do_cciss_intr
    >>>>>>>
    >>>>>>> On Thu, 25 Sep 2008 13:33:07 -0700 Randy Dunlap wrote:
    >>>>>>>
    >>>>>>>> Jens Axboe wrote:
    >>>>>>>>> On Thu, Sep 04 2008, Miller, Mike (OS Dev) wrote:
    >>>>>>>>>>>>>> 0x3bb2 <do_cciss_intr+1649>: mov 0x2(%r8),%dx
    >>>>>>>>>>>>>> 0x3bb7 <do_cciss_intr+1654>: test %dx,%dx
    >>>>>>>>>>>>>> 0x3bba <do_cciss_intr+1657>: je 0x3f0e
    >>>>>>> <do_cciss_intr+2509>
    >>>>>>>>>>>>>> $ addr2line -e cciss.o -f do_cciss_intr+0x627
    >>>>>>>>>>>>>> SA5_fifo_full
    >>>>>>>>>>>>>>
    >> /home/rdunlap/linsrc/linux-2.6.27-rc3-git7/drivers/block/cciss.h:
    >>>>>>> 2
    >>>>>>>>>>> 06
    >>>>>>>>>>>>> OK ...that's confusing. It seems to be saying that
    >>>>>>> ctrlr_info_t
    >>>>>>>>>>>>> * was NULL. However, I can't see a way of
    >> getting into the
    >>>>>>>>>>> fifo_full
    >>>>>>>>>>>>> callback from do_cciss_intr ..
    >>>>>>>>>>>>> especially not with an NULL host.
    >>>>>>>>>>>>>
    >>>>>>>>>>>>> James
    >>>>>>>>>>>> That is weird. Even if we could get there
    >> fifo_full doesn't
    >>>>>>>>>>> do anything but wait for a bit.
    >>>>>>>>>>>
    >>>>>>>>>>> Hi,
    >>>>>>>>>>>
    >>>>>>>>>>> This just happened again. This time it's on
    >> 2.6.27-rc5-git3.
    >>>>>>>>>>> ~Randy
    >>>>>>>>>> Thanks Randy. I think. :)
    >>>>>>>>>>
    >>>>>>>>>> I'll try to recreate in my lab.
    >>>>>>>>> This looks somewhat strange, mostly like 'c' is NULL
    >> and it's
    >>>>>>>>> oopsing in in removeQ (I don't think Randy's analysis is
    >>>>>>> correct in
    >>>>>>>>> assuming it's 'h' and it's in fifo_full). Given that 'c'
    >>>>>>> cannot be
    >>>>>>>>> NULL, it's c->prev or c->next that are NULL.
    >>>>> This BUG: has happened (now) 5 times today. Higher
    >> frequency than
    >>>>> usual for some reason.
    >>>>>
    >>>>> I enabled CCISS_DEBUG and added one printk in removeQ(). On the
    >>>>> first call
    >>>> s/first/second/
    >>>>
    >>>>
    >>>>> to removeQ(), both c->next and c->prev are NULL.
    >>>>>
    >>>>> Here's the kernel log output from cciss:
    >>> I added a printk() in addQ() as well. Here's the new output:
    >>>
    >>> HP CISS Driver (v 3.6.20)
    >>> ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 54 cciss
    >> 0000:42:08.0:
    >>> PCI INT A -> Link[LNKA] -> GSI 54 (level, high) -> IRQ 54 command =
    >>> 147 irq = 36 board_id = 3211103c cciss 0000:42:08.0: irq 87 for
    >>> MSI/MSI-X address 0 = fdf80000 cfg base address = 10 cfg
    >> base address
    >>> index = 0 cfg offset = 400 Controller Configuration information
    >>> ------------------------------------
    >>> Signature = CISS
    >>> Spec Number = 1
    >>> Transport methods supported = 0x6
    >>> Transport methods active = 0x3
    >>> Requested transport Method = 0x0
    >>> Coalesce Interrupt Delay = 0x0
    >>> Coalesce Interrupt Count = 0x1
    >>> Max outstanding commands = 0x256
    >>> Bus Types = 0x200000
    >>> Server Name =
    >>> Heartbeat Counter = 0x1672
    >>>
    >>>
    >>> Trying to put board into Simple mode
    >>> I counter got to 1 0
    >>> Controller Configuration information
    >>> ------------------------------------
    >>> Signature = CISS
    >>> Spec Number = 1
    >>> Transport methods supported = 0x6
    >>> Transport methods active = 0x3
    >>> Requested transport Method = 0x0
    >>> Coalesce Interrupt Delay = 0x0
    >>> Coalesce Interrupt Count = 0x1
    >>> Max outstanding commands = 0x256
    >>> Bus Types = 0x200000
    >>> Server Name =
    >>> Heartbeat Counter = 0x1672
    >>>
    >>>
    >>> cciss0: <0x3238> at PCI 0000:42:08.0 IRQ 87 using DAC
    >>> cciss: intr_pending 8
    >>> cciss: addQ: Qptr=ffff88027e0100b8, c=ffff88007f83e000
    >>> cciss: removeQ: Qptr=ffff88027e0100b8, c=ffff88007f83e000,
    >>> next=ffff88007f83e000, prev=ffff88007f83e000 Sending
    >> 7f83e000 - down
    >>> to controller
    >>> cciss: addQ: Qptr=ffff88027e0100c0, c=ffff88007f83e000
    >>> cciss: intr_pending 8
    >>> cciss: Read 4 back from board
    >>> cciss: removeQ: Qptr=ffff88027e0100c0, c=ffff88007f840000,
    >>> next=0000000000000000, prev=0000000000000000
    >>> BUG: unable to handle kernel NULL pointer dereference at
    >>> 0000000000000248
    >> Randy, can you post the debug patch you used? The above goes
    >> boom when it attempts to remove a command that isn't on the
    >> list, the Qptr in the last example should be empty, hence the
    >> oops. So I'd be interested in seeing what removeQ() calls
    >> this is, I'm assuming it's this bit in
    >> do_cciss_intr():
    >>
    >> ...
    >> while (c->busaddr != a) {
    >> c = c->next;
    >> if (c == h->cmpQ)
    >> break;
    >> }
    >> }
    >> /*
    >> * If we've found the command, take it off the
    >> * completion Q and free it
    >> */
    >> if (c->busaddr == a) {
    >> removeQ(&h->cmpQ, c);
    >> if (c->cmd_type == CMD_RWREQ) {
    >> complete_command(h, c, 0);
    >> ...
    >>
    >> If so, what part of the c lookup are you hitting - the on that does:
    >>
    >> c = h->cmd_pool + a2;
    >>
    >> or the c->busaddr check that his shown above?
    >>
    >> --
    > Randy,
    > I still can't reproduce this bug. I have your config file on a BL465c w/e200i. Just to confirm, you only see this at init time, correct?

    Yes, only at init time.

    > Please post your debug patch as Jens requested.

    Done (separately).

    I need to back up a bit. Yesterday these BUGs happened consistenly,
    so I wondered why. Then I recalled that for debugging another bug/problem,
    I had changed the test system's normal boot kernel from 2.6.25 to
    2.6.18-8. The test system is used to build and then boot the new kernel
    *via kexec*, so it's quite possible (or certain) that something in the kexec
    world has been fixed since 2.6.18. I don't recall seeing this problem
    lately when using 2.6.25 to kexec/boot the new test kernel, so I'm quite
    willing to drop the bug for now and then re-open it if I see the problem
    again. OK??

    --
    ~Randy


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