linux-kernel - Re: [PATCH 2/2] sata_sil: disable DMA engine in ->freeze

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Date:	Wed, 08 Apr 2009 15:49:57 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Dustin Harrison <d.harrison@...us.com>,
	Tejun Heo <htejun@...il.com>
CC:	Sagar Borikar <sagar.borikar@...il.com>, linux-ide@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH 2/2] sata_sil: disable DMA engine in ->freeze

Dustin Harrison wrote:
> Jeff Garzik wrote:
>> Sagar Borikar wrote:
>>> This patch works for our platform.
>>
>> Did you try both patches together?  Both are required for the solution.
>>
> Thanks for updating the patch Jeff.  I see you spotted the reason why I 
> didn't put the code into sil_freeze.  I tested your patch and it 
> prevented the kernel panic.  I now get the following output, which seems 
> to be correct to me.
> 
> WARNING: at drivers/ata/libata-core.c:5209 ata_qc_complete()

hum, my patch would indeed trigger this WARN_ON_ONCE() in ata_qc_complete():

         if (ap->ops->error_handler) {
                 struct ata_device *dev = qc->dev;
                 struct ata_eh_info *ehi = &dev->link->eh_info;

                 WARN_ON_ONCE(ap->pflags & ATA_PFLAG_FROZEN);

Tejun, was that WARN_ON() originally added to detect spurious callers? 
Or, completions after the EH started?

AFAICS, libata still owns the qc's at this point, so it should not be a 
problem to complete them when the port is frozen.

	Jeff




> Call Trace:
> [<80107ed0>] dump_stack+0x8/0x34
> [<802f92e0>] ata_qc_complete+0x58/0x114
> [<80303aec>] ata_port_abort+0xc4/0x104
> [<80306870>] sil_interrupt+0x340/0x384
> [<80146cc0>] handle_IRQ_event+0x54/0xb8
> [<80146dc0>] __do_IRQ+0x9c/0x11c
> [<80102670>] ll_sutuspci_irq+0xe8/0x158
> [<8010161c>] do_extended_irq+0xa0/0x104
> [<80102b94>] ret_from_irq+0x0/0x4
> [<8029c4fc>] both_aligned+0x1c/0x64
> [<8014a9a4>] file_read_actor+0xac/0x154
> [<8014a564>] do_generic_mapping_read+0x210/0x5a4
> [<8014ce98>] generic_file_aio_read+0x180/0x1d4
> [<8016cba4>] do_sync_read+0xc4/0x128
> [<8016ccbc>] vfs_read+0xb4/0x154
> [<8016d02c>] sys_read+0x54/0x98
> [<8010a620>] stack_done+0x20/0x3c
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