Jens Axboe wrote:
> 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

Sure.  I have 2 patches.  One is a fix for CCISS_DEBUG printk formats that I
posted to linux-scsi yesterday.  The other just adds more debug code.

> 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?

I don't know that the patch will tell us which call it is.
The added code is inside removeQ() and addQ(), not near the calls
to them.

-- 
~Randy