linux-kernel - Re: [PATCH] libata: Register for dock events when the drive is inside a dock station

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Message-ID: <20080311235548.GA4089@homac>
Date:	Wed, 12 Mar 2008 00:55:49 +0100
From:	Holger Macht <hmacht@...e.de>
To:	Tejun Heo <htejun@...il.com>
Cc:	Jeff Garzik <jeff@...zik.org>, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org,
	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
Subject: Re: [PATCH] libata: Register for dock events when the drive is
	inside a dock station

On Tue 04. Mar - 13:12:54, Tejun Heo wrote:
> Holger Macht wrote:
> > On Thu 28. Feb - 19:32:43, Holger Macht wrote:
> >> On Thu 28. Feb - 16:58:17, Holger Macht wrote:
> >>> On Thu 28. Feb - 22:05:53, Tejun Heo wrote:
> >>>> Holger Macht wrote:
> >>>>> On Thu 28. Feb - 18:35:06, Tejun Heo wrote:
> >>>>>> Holger Macht wrote:
> >>>>>>> The hotplug handler is only called if the device is actually inside the
> >>>>>>> dock station. If it is not, nothing will happen. I hope that I got your
> >>>>>>> question right?
> >>>>>> Yes, right.
> >>>>>>
> >>>>>>> However, if this would be helpful, it would be easy to add something like
> >>>>>>> a am_I_on_dock_station?(...) function to the dock driver.
> >>>>>> Hmm.. as long as the event is only delivered when the device is actually
> >>>>>> connected behind dock, I think it's okay.
> >>>>> The dock driver also export a is_dock_device(acpi_handle) function, which
> >>>>> could be used to make more fine-grained decisions, but it shouldn't be
> >>>>> needed here.
> >>>>>
> >>>>>> Does the attached patch fix the previous undock problem?  It now
> >>>>>> explicitly tells libata EH to detach the notified devices on
> >>>>>> EJECT_REQUEST and wait for EH to complete such that control is returned
> >>>>>> to ACPI after all notified devices are actually detached.
> >>>>> No it does not. Apparently, it freezes faster (from 1 second down to
> >>>>> immediately). Before, it just froze when someone (in this case HAL) tried
> >>>>> to access the device. The "echo 1 > undock" call does not even return, so
> >>>>> it might have introduced another problem.
> >>>> The code should be in generally right direction.  Can you be persuaded
> >>>> into tracking down what's going on?
> >>> I had a quick glance with adding some printk's. Now I got a different
> >>> behaviour once. System did not freeze, but were certainly confused. The
> >>> last thing which got printed to messages was exactly before
> >>> spin_lock_irqsave(ap->lock, flags); at the beginning of ata_acpi_handle_hotplug(...)
> >>>
> >>> The printk immediately after this call didn't come through anymore (with
> >>> being able to use the system for a short time afterwards).
> >> Ok, it seems that there is something broken somewhere else in
> >> 2.6.25.rc3. Not sure at all if it's your patch freezing the machine. I'll
> >> give 2.6.24.3 a try...
> > 
> > So once again...
> > 
> > After applying your patch, I got the OOPS seen in attachment
> > 'oops-undock-1'. After changing the following, which is hopefully
> > correct...
> > 
> > --- ../orig/linux-2.6.24.3/drivers/ata/libata-acpi.c	2008-02-29 00:31:44.000000000 +0100
> > +++ drivers/ata/libata-acpi.c	2008-02-29 00:32:26.000000000 +0100
> > @@ -123,7 +123,7 @@
> >  {
> >  	char event_string[12];
> >  	char *envp[] = { event_string, NULL };
> > -	struct ata_eh_info *ehi = &ap->link.eh_info;
> > +	struct ata_eh_info *ehi;
> >  	struct kobject *kobj = NULL;
> >  	int wait = 0;
> >  	unsigned long flags;
> > @@ -131,6 +131,8 @@
> >  	if (!ap)
> >  		ap = dev->link->ap;
> >  
> > +	ehi = &ap->link.eh_info;
> > +
> >  	spin_lock_irqsave(ap->lock, flags);
> >  
> >  	switch (event) {
> > 
> > 
> > ...I got both an oops when docking (attachments oops-dock) and when undocking
> > (attachment oops-undock2).
> 
> Yeah, that was one mistake.  There's another.
> 
> +#if defined(CONFIG_ACPI_DOCK) || defined(CONFIG_ACPI_DOCK_MODULE)
> +				/* we might be on a docking station */
> +				register_hotplug_dock_device(ap->acpi_handle,
> +							     ata_acpi_dev_notify,
> +							     ap);
> +#endif
> 
> dev_notify is being registered with a pointer to ap.  No wonder it causes

It seems this change is missing from your patch. I've attached a fixed
version...

> strange dereferences later on.  Attached is the fixed patch.  Can you
> please give it a shot?

...and now the good news...the new patch works flawlessly with
2.6.25-rc5...

undocking...
ata5.00: disabled
ata5.00: detaching (SCSI 4:0:0:0)
ACPI: \_SB_.GDCK - undocking
usb 1-6: USB disconnect, address 5

docking...
ACPI: \_SB_.GDCK - docking
ata5: exception Emask 0x10 SAct 0x0 SErr 0x0 action 0xa frozen
ata5: ACPI event
ata5: soft resetting link
ata5.00: ATAPI: HL-DT-ST DVDRAM GSA-4083N, 1.08, max UDMA/33
ata5.00: configured for UDMA/33
ata5: exception Emask 0x10 SAct 0x0 SErr 0x0 action 0x1 t4
ata5: ACPI event
ata5: soft resetting link
ata5.00: configured for UDMA/33
ata5: EH complete
scsi 4:0:0:0: CD-ROM            HL-DT-ST DVDRAM GSA-4083N 1.08 PQ: 0 ANSI: 5
sr0: scsi3-mmc drive: 24x/24x writer dvd-ram cd/rw xa/form2 cdda tray
sr 4:0:0:0: Attached scsi CD-ROM sr0
sr 4:0:0:0: Attached scsi generic sg1 type 5

Thanks,
	Holger

View attachment "libata-add-hotplug-support.patch" of type "text/x-patch" (3763 bytes)