linux-kernel - Re: [PATCH] libata: Forcing PIO0 mode on reset must not freeze system

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Date:	Mon, 11 Feb 2008 15:06:03 +0100
From:	Holger Macht <hmacht@...e.de>
To:	Tejun Heo <htejun@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	alan@...hat.com, jeff@...zik.org,
	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
Subject: Re: [PATCH] libata: Forcing PIO0 mode on reset must not freeze
	system

On Mon 11. Feb - 22:11:32, Tejun Heo wrote:
> Holger Macht wrote:
> >> It should be called via ata_acpi_{ap|dev}_notify() callbacks installed
> >> via acpi_install_notify_handler().  Can you add dump_stack() in the
> >> function and verify that it actually is being called?  It could be that
> >> the method is called too late or libata takes too long to actually
> >> unplug the device.  Hmmm... It seems what ata_acpi_handle_hotplug() does
> >> isn't enough for undock.  It probably should request detaching the
> >> device instead of just notifying hotplug event.  Anyways, please lemme
> >> know whether and when the function is called.
> > 
> > I already checked, it's never called AFAICS. And I couldn't find a place
> > where it should be installed, otherwise, I would have sent a patch. The
> > dock driver already calls the notify methods on devices in the dock
> > station before doing the real undock.
> 
> ata_acpi_associate() calls acpi_install_notify_handler() for each
> device.  Isn't that enough?

It should be. I tried once more and noticed that
ata_acpi_handle_hotplug(...) is called when the cdrom is about to be
removed via the bay driver (just removing the device, not the whole dock
station). Actually there is a connection between the bay and the dock
driver, and one of them should notice that the cdrom/bay device is
dependent on the dock, but I don't know what's going wrong here. Kristen
(CC) should definitely know more about this interaction...

On a related note, shouldn't ata_acpi_handle_hotplug delete the device
like what is done when doing

  echo 1 > /sys/devices/.../block/sr0/device/delete

?

Regards,
	Holger
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