Re: [PATCH 25/30] ACPI / hotplug / PCI: Check for new devices on enabled slots

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday, September 05, 2013 09:11:51 AM Lan Tianyu wrote:
> 2013/9/5 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Thursday, September 05, 2013 02:17:06 PM Lan Tianyu wrote:
> >> 2013/9/5 Alex Williamson <alex.williamson@redhat.com>:
> >> > On Thu, 2013-09-05 at 01:35 +0200, Rafael J. Wysocki wrote:
> >> >> On Wednesday, September 04, 2013 05:12:14 PM Alex Williamson wrote:
> >> >> > On Thu, 2013-09-05 at 00:54 +0200, Rafael J. Wysocki wrote:
> >> >> > > On Wednesday, September 04, 2013 02:36:34 PM Alex Williamson wrote:
> >> >> > > > On Thu, 2013-07-18 at 01:32 +0200, Rafael J. Wysocki wrote:
> >> >> > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> >> > > > >
> >> >> > > > > The current implementation of acpiphp_check_bridge() is pretty dumb:
> >> >> > > > >  - It enables a slot if it's not enabled and the slot status is
> >> >> > > > >    ACPI_STA_ALL.
> >> >> > > > >  - It disables a slot if it's enabled and the slot status is not
> >> >> > > > >    ACPI_STA_ALL.
> >> >> > > > >
> >> >> > > > > This behavior is not sufficient to handle the Thunderbolt daisy
> >> >> > > > > chaining case properly, however, because in that case the bus
> >> >> > > > > behind the already enabled slot needs to be rescanned for new
> >> >> > > > > devices.
> >> >> > > > >
> >> >> > > > > For this reason, modify acpiphp_check_bridge() so that slots are
> >> >> > > > > disabled and stopped if they are not in the ACPI_STA_ALL state.
> >> >> > > > >
> >> >> > > > > For slots in the ACPI_STA_ALL state, devices behind them that don't
> >> >> > > > > respond are trimmed using a new function, trim_stale_devices(),
> >> >> > > > > introduced specifically for this purpose.  That function walks
> >> >> > > > > the given bus and checks each device on it.  If the device doesn't
> >> >> > > > > respond, it is assumed to be gone and is removed.
> >> >> > > > >
> >> >> > > > > Once all of the stale devices directy behind the slot have been
> >> >> > > > > removed, acpiphp_check_bridge() will start looking for new devices
> >> >> > > > > that might have appeared on the given bus.  It will do that even if
> >> >> > > > > the slot is already enabled (SLOT_ENABLED is set for it).
> >> >> > > > >
> >> >> > > > > In addition to that, make the bus check notification ignore
> >> >> > > > > SLOT_ENABLED and go for enable_device() directly if bridge is NULL,
> >> >> > > > > so that devices behind the slot are re-enumerated in that case too.
> >> >> > > > >
> >> >> > > > > This change is based on earlier patches from Kirill A Shutemov
> >> >> > > > > and Mika Westerberg.
> >> >> > > > >
> >> >> > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> >> > > > > Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> >> >> > > > > ---
> >> >> > > >
> >> >> > > > FYI, git bisect landed on this patch as the cause of my serial console
> >> >> > > > dying on current upstream.  Further debugging to come...  Thanks,
> >> >> > >
> >> >> > > Well, sorry about that.
> >> >> > >
> >> >> > > What exactly do you mean by "dying"?
> >> >> >
> >> >> > Sorry, I was hoping to have more details quickly, but it's been a pain
> >> >> > to debug.  By dying I mean serial console output suddenly stops during
> >> >> > kernel boot and nothing more comes out of it until after the system is
> >> >> > rebooted.  The problem happens when acpiphp_check_bridge() calls
> >> >> > enable_slot().  The serial console dies somewhere down in
> >> >> > acpiphp_bus_trim().  I think this is happening on the 00:1f ISA bridge,
> >> >> > so there's a good chance the serial ports are described as somewhere
> >> >> > under there.
> >> >>
> >> >> Can you please check if that is the acpiphp_bus_trim() called by
> >> >> acpiphp_bus_add() or the other one called from trim_stale_devices()?
> >> >>
> >> >> Just add a dump_stack() or WARN_ON(1) to trim_stale_devices() next to
> >> >> the acpiphp_bus_trim() call and see if that triggers.  I *think* it's the one
> >> >> in acpiphp_bus_add(), but it won't hurt to verify that.
> >> >
> >> > Here's the call path:
> >> >
> >> > [   16.120824]  [<ffffffff81627e6c>] dump_stack+0x55/0x76
> >> > [   16.125979]  [<ffffffff8162132e>] enable_slot+0x4ee/0x5e0
> >> > [   16.131396]  [<ffffffff813418fb>] ? trim_stale_devices+0x5b/0xf0
> >> > [   16.137420]  [<ffffffff81341b35>] acpiphp_check_bridge+0xd5/0x110
> >> > [   16.143531]  [<ffffffff81342acb>] hotplug_event+0x16b/0x260
> >> > [   16.149115]  [<ffffffff81072cd9>] ? process_one_work+0x189/0x540
> >> > [   16.155136]  [<ffffffff81342bf0>] hotplug_event_work+0x30/0x70
> >> > [   16.160978]  [<ffffffff81072d3b>] process_one_work+0x1eb/0x540
> >> > [   16.166819]  [<ffffffff81072cd9>] ? process_one_work+0x189/0x540
> >> > [   16.172836]  [<ffffffff8107353c>] worker_thread+0x11c/0x370
> >> > [   16.178426]  [<ffffffff81073420>] ? rescuer_thread+0x350/0x350
> >> > [   16.184276]  [<ffffffff8107b0ea>] kthread+0xea/0xf0
> >> > [   16.189165]  [<ffffffff8107b000>] ? kthread_create_on_node+0x160/0x160
> >> > [   16.195700]  [<ffffffff816395dc>] ret_from_fork+0x7c/0xb0
> >> > [   16.201109]  [<ffffffff8107b000>] ? kthread_create_on_node+0x160/0x160
> >> >
> >> > The actual death of the serial console occurs in acpi_device_set_power()
> >> > called from:
> >> >
> >> > enable_slot()
> >> >  acpiphp_bus_add()
> >> >   acpiphp_bus_trim()
> >> >    acpi_bus_trim()
> >> >     acpi_walk_namespace()
> >> >      acpi_bus_remove()
> >> >       acpi_device_unregister()
> >> >        acpi_device_set_power()
> >> >
> >> > I can't seem to get a path from the acpi devices in question there, so I
> >> > have no idea what's getting trimmed here.  It worries me quite a bit by
> >> > introducing this trimming that apparently wasn't happening before
> >> > though.  Thanks,
> >>
> >> Hi Alex:
> >>            Could you apply the following patch and bootup with kernel param
> >> "acpiphp.acpiphp_debug=1"?
> >>            I guess the patch can make serial port alive. It will not
> >> be put into D3cold
> >> during trimming. But I don't know why it doesn't work after being put
> >> back to D0.
> >
> > Do we actually put it into D0 in acpi_bus_scan()?  I don't think so.
> >
> 
> Hi Rafael:
>          I mean the code in the acpiphp_bus_add(). After trimming and acpi
> bus scan handle, the device will be put back to D0 if acpi_bus_get_device()
> return acpi device. So I thought the serial port is put back to D0.

*The* device corresponding to handle will be put into D0.  Any devices below it
whose ACPI device objects may also be added by acpi_bus_scan() - not necessarily.

Thanks,
Rafael