Re: Hang during boot, bisected to commit 96d60303fd

[Robert Hancock]

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..
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