linux-kernel - Re: Hang during boot, bisected to commit 96d60303fd

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Message-ID: <AANLkTikpv86r5BBPCEOHujpm8uCgY0DxghSKjBufBWiM@mail.gmail.com>
Date:	Thu, 3 Jun 2010 21:21:36 -0400
From:	Marc Dionne <marc.c.dionne@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org, garzik@...hat.com
Subject: Re: Hang during boot, bisected to commit 96d60303fd

On Wed, Jun 2, 2010 at 10:00 PM, Matthew Garrett <mjg59@...f.ucam.org> 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@...f.ucam.org

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.

Marc

Download attachment "bad_ahci_dmesg" of type "application/octet-stream" (50274 bytes)

Download attachment "normal_ahci_dmesg" of type "application/octet-stream" (49825 bytes)