Re: in 2.6.23-rc3-git7 in do_cciss_intr

[Randy Dunlap <randy.dunlap@oracle.com>]

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