Re: 2.6.36: Dropped interrupts in ata_piix

[Mike Waychison <mikew@google.com>]

Tejun Heo wrote:
> (cc'ing linux-ide)
> 
> Hello,
> 
> On 10/25/2010 08:13 PM, Mike Waychison wrote:
>> I'm having problems reliably booting 2.6.36 on one of my development
>> systems whereby it looks like the ata_piix driver isn't
>> acknowledging interrupts.
> 
> Why do you think ata_piix isn't ack'ing IRQs?

Well, it's the only thing in the logs marked up as using IRQ 20.

> 
>> I went through a bit of the recent history here, and it seems that
>> things clear up for me if I revert the following two commits in my
>> tree:
>>
>> 1c5afdf7 "libata-sff: separate out BMDMA init"
>> c3b28894 "libata-sff: separate out BMDMA irq handler"
> 
> Those commits look scary but they're code refactoring in nature and
> unless I screwed up (definitely possible) things shouldn't break over
> them.  Another thing is that they have been in mainline for quite some
> time and even shipped with ubuntu 10.10 and this is the first report,
> so I'm a bit skeptical they actually are the culprit.

Ya, I don't see how they change anything either, but I can't pretend to 
really understand what is going on in this code either :(

> 
>> I usually don't get a trace, but I did get this blurted out once on
>> the console:
>>
>> kinit: Mounted root (ext2 filesystem) readonly.
>> INIT: version 2.78 booting
>> [    5.419165] irq 20: nobody cared (try booting with the "irqpoll" option)
>> [    5.420140] Pid: 0, comm: kworker/0:1 Not tainted 2.6.36-smp-mikew #5gca29cdd
>> [    5.420140] Call Trace:
>> [    5.420140]  <IRQ>  [<ffffffff810b207f>] __report_bad_irq+0x3d/0x8c
>> [    5.420140]  [<ffffffff810b21e6>] note_interrupt+0x118/0x17e
>> [    5.420140]  [<ffffffff810b29be>] handle_fasteoi_irq+0xa7/0xcc
>> [    5.420140]  [<ffffffff81032da5>] handle_irq+0x24/0x2f
>> [    5.420140]  [<ffffffff81453744>] do_IRQ+0x5c/0xc3
>> [    5.420140]  [<ffffffff8144d853>] ret_from_intr+0x0/0xa
>> [    5.420140]  <EOI>  [<ffffffff81037a64>] ? mwait_idle+0x93/0x9b
>> [    5.420140]  [<ffffffff81037a0a>] ? mwait_idle+0x39/0x9b
>> [    5.420140]  [<ffffffff8102faee>] cpu_idle+0x63/0xd5
>> [    5.420140]  [<ffffffff8193d340>] start_secondary+0x192/0x196
>> [    5.420140] handlers:
>> [    5.420140] [<ffffffff812e26e6>] (ata_bmdma_interrupt+0x0/0x17)
>> [    5.420140] Disabling IRQ #20
>> [   34.720103] ata1: lost interrupt (Status 0x51)
>> [   34.724569] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
>> [   34.731612] ata1.00: BMDMA stat 0x26, BMDMA stat 0x0, BMDMA stat 0x0, BMDMA stat 0x0, BMDMA stat 0x0
>> [   34.740750] ata1.00: failed command: READ DMA
>> [   34.745115] ata1.00: cmd c8/00:a0:f7:78:09/00:00:00:00:00/e0 tag 0 dma 81920 in
>> [   34.745116]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x24 (host bus error)
> 
> Hmm... this is interesting.  The IRQ storm happened while a read
> command was in progress.  BMDMA indicates that host bus error occurred
> (the DMA controller experienced transfer failure on the PCI side while
> trying to write to main memory).  It's curious why the interrupt
> handler thought the IRQ wasn't its.  ata_bmdma_port_intr() should have
> noticed ATA_DMA_INTR and the command should have been completed
> immediately, weird.

To be clear, usually all I see on the console when hanging is:

[   15.411337] Disabling IRQ #20

I've only ever had the above call trace make it out to console once.

Sometimes this happens while mounting the root filesystem, mounting the 
second filesystem (on the same disk) or while loading modules.  I don't 
think the failure is tied to any particular sector.

I don't have any trouble with previous kernels (2.6.34 was fine), and 
backing out the above two commits makes the symptom go away.

> 
>> [   34.760490] ata1.00: status: { DRDY }
>> [   34.764180] ata1: soft resetting link
>> [   35.143059] ata1.00: configured for UDMA/133
>> [   35.147332] ata1.00: device reported invalid CHS sector 0
>> [   35.152730] ata1: EH complete
>>
>> As you can see above, something looks to be wrong with ata_bmdma_interrupt.
>>
>> Have you seen this problem before?
> 
> No, this is the first time and your hardware seems to be developing an
> interesting issue.  I suggest trying a different PSU if you have one
> available.  That said, it would still be useful to track down why the
> error handling isn't working as expected.  How reliably can you
> reproduce the problem?


I can reproduce very reliably on this machine in particular.  I have 
other machines of similar type that seem to be fine (though I need to 
dig into the test result database to be sure).  I'd be happy to try any 
suggestions on this machine.