On Thu, Jun 3, 2010 at 11:42 PM, Robert Hancock <hancockrwd@xxxxxxxxx> wrote:
> On 06/03/2010 07:21 PM, Marc Dionne wrote:
>>
>> On Wed, Jun 2, 2010 at 10:00 PM, Matthew Garrett<mjg59@xxxxxxxxxxxxx>
>> wrote:
>>>
>>> On Wed, Jun 02, 2010 at 09:49:27PM -0400, Marc Dionne wrote:
>>>>
>>>> Since somewhere early in the 2.6.35 merge window I've been seeing a
>>>> hang
>>>> during boot. The hang last roughly 30 seconds and is followed by
>>>> this:
>>>>
>>>> ata4.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x6 frozen
>>>> ata4.00: failed command: READ FPDMA QUEUED
>>>> ata4.00: cmd 60/08:00:00:00:00/00:00:00:00:00/40 tag 0 ncq 4096 in
>>>> res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
>>>> ata4.00: status: { DRDY }
>>>> ata4: hard resetting link
>>>> ahci_is_device_present: status is: 80
>>>> ahci_is_device_present: status(2) is: 3
>>>> ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
>>>> ata4.00: configured for UDMA/133
>>>> ata4.00: device reported invalid CHS sector 0
>>>> ata4: EH complete
>>>>
>>>> The system works normally once booted. I had some time to do a
>>>> bisect
>>>> today and it cleanly ended up pointing to this commit:
>>>> 96d60303fd: ahci: Turn off DMA engines when there's no device
>>>> attached
>>>>
>>>> Reverting the commit makes the system boot cleanly as before. System
>>>> has
>>>> an Intel ICH10 based board, in AHCI mode, disk is an Intel X25M SSD.
>>>
>>> Hm, interesting. Jeff, any immediate ideas? I don't see this behaviour
>>> on my ICH10. Is there actually a device on ata4?
>>>
>>> --
>>> Matthew Garrett | mjg59@xxxxxxxxxxxxx
>>
>> If it's helpful, attached are the dmesg output following a normal boot
>> and one with the hang.
>>
>> The only difference in the kernel used for those two boots is that the
>> return statement in ahci_start_engine following the call to
>> ahci_is_device_present is commented out for the normal boot case.
>> When the return statement is active, the 30 second hang occurs.
>
> Can you try and put a printk in where it's returning out of the
> ahci_start_engine method? I wonder if that's getting triggered somewhere
> unexpected..
Attached is a dmesg output with some printks added to show the status
when ahci_is_device_present causes ahci_start_engine to return early..
It looks to me like there's two passes through ahci_start_engine for
all ports, and during the first pass the port with the disk is showing
a status of 127, causing the function to return early and skipping the
start DMA part. This seems to cause the hang later on.
I noticed that during this first pass all the print_id fields for the
ports are still set to -1, so as a test I made ahci_start_engine only
do the check for ahci_is_device_present if print_id != -1, and this
makes the system boot normally.
Marc
Attachment:
dmesg_ahci
Description: Binary data
