Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753979Ab0FEBhb (ORCPT ); Fri, 4 Jun 2010 21:37:31 -0400 Received: from mail-iw0-f174.google.com ([209.85.214.174]:41432 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752731Ab0FEBh1 convert rfc822-to-8bit (ORCPT ); Fri, 4 Jun 2010 21:37:27 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=HgsDlDOekIbxTORf69m8GFoNtx7AdnAgtgahrQnGTQigeq/p9gz/rI5lDgnm9bz73+ U/mqaE7Q0KNpruoVYIQhAlcWoUbt+lo4J8xG7QlTBjfynis8PV01jSjV/Omeax+Q/Ut+ qECd+sLbhxwjouQzs26GAQvj5gyRLjpv5UHbo= MIME-Version: 1.0 In-Reply-To: References: <20100603020006.GB19123@srcf.ucam.org> <4C08760B.8050002@gmail.com> Date: Fri, 4 Jun 2010 19:37:27 -0600 Message-ID: Subject: Re: Hang during boot, bisected to commit 96d60303fd From: Robert Hancock To: Marc Dionne Cc: Matthew Garrett , Linux Kernel Mailing List , linux-ide@vger.kernel.org, garzik@redhat.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3445 Lines: 76 Fri, Jun 4, 2010 at 7:23 PM, Marc Dionne wrote: > On Thu, Jun 3, 2010 at 11:42 PM, Robert Hancock wrote: >> On 06/03/2010 07:21 PM, Marc Dionne wrote: >>> >>> On Wed, Jun 2, 2010 at 10:00 PM, Matthew Garrett >>> ?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@srcf.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. >> >> 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. Is that the right dmesg? I didn't see where the extra output was. It might be useful to put a WARN_ON(1); inside ahci_start_engine to see the two code paths where it's being called.. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/