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Date: Thu, 05 Sep 2013 23:43:45 +0200 From: "Rafael J. Wysocki" <rjw@...k.pl> To: Lan Tianyu <lantianyu1986@...il.com> Cc: Alex Williamson <alex.williamson@...hat.com>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, LKML <linux-kernel@...r.kernel.org>, Linux PCI <linux-pci@...r.kernel.org>, Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>, Mika Westerberg <mika.westerberg@...ux.intel.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: Re: [PATCH 25/30] ACPI / hotplug / PCI: Check for new devices on enabled slots On Thursday, September 05, 2013 09:11:51 AM Lan Tianyu wrote: > 2013/9/5 Rafael J. Wysocki <rjw@...k.pl>: > > On Thursday, September 05, 2013 02:17:06 PM Lan Tianyu wrote: > >> 2013/9/5 Alex Williamson <alex.williamson@...hat.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@...el.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@...el.com> > >> >> > > > > Tested-by: Mika Westerberg <mika.westerberg@...ux.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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