From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH 25/30] ACPI / hotplug / PCI: Check for new devices on enabled slots Date: Thu, 05 Sep 2013 13:54:57 +0200 Message-ID: <3752304.TvOhsce0U1@vostro.rjw.lan> References: <26431283.HJCKsss0rt@vostro.rjw.lan> <1378352279.3246.183.camel@ul30vt.home> <1378353962.3246.192.camel@ul30vt.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <1378353962.3246.192.camel@ul30vt.home> Sender: linux-pci-owner@vger.kernel.org To: Alex Williamson Cc: ACPI Devel Maling List , Bjorn Helgaas , LKML , Linux PCI , Yinghai Lu , Jiang Liu , Mika Westerberg , "Kirill A. Shutemov" List-Id: linux-acpi@vger.kernel.org On Wednesday, September 04, 2013 10:06:02 PM Alex Williamson wrote: > On Wed, 2013-09-04 at 21:37 -0600, Alex Williamson wrote: > > 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 > > > > > > > > > > > > > > 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 > > > > > > > Tested-by: Mika Westerberg > > > > > > > --- > > > > > > > > > > > > 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] [] dump_stack+0x55/0x76 > > [ 16.125979] [] enable_slot+0x4ee/0x5e0 > > [ 16.131396] [] ? trim_stale_devices+0x5b/0xf0 > > [ 16.137420] [] acpiphp_check_bridge+0xd5/0x110 > > [ 16.143531] [] hotplug_event+0x16b/0x260 > > [ 16.149115] [] ? process_one_work+0x189/0x540 > > [ 16.155136] [] hotplug_event_work+0x30/0x70 > > [ 16.160978] [] process_one_work+0x1eb/0x540 > > [ 16.166819] [] ? process_one_work+0x189/0x540 > > [ 16.172836] [] worker_thread+0x11c/0x370 > > [ 16.178426] [] ? rescuer_thread+0x350/0x350 > > [ 16.184276] [] kthread+0xea/0xf0 > > [ 16.189165] [] ? kthread_create_on_node+0x160/0x160 > > [ 16.195700] [] ret_from_fork+0x7c/0xb0 > > [ 16.201109] [] ? 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, > > As suspected, the pnp.bus_id/id of the last device before the serial > console dies is COM1/PNP0501. I also see all of these being trimmed > out: > > MBRD/PNP0C02 > DMAC/PNP0200 > MATH/PNP0C04 > PIC/PNP0000 > HPET/PNP0103 > RTC/PNP0B00 > SPKR/PNP0800 > TIME/PNP0100 > LNK{A-H}/PNP0C0F > > This seems like a bad idea. I forgot to mention, the original > hotplug_event is called with a device check on \_SB_.PCI0.PEX2. The box > where I'm seeing this is a pretty generic X58 based Nehalem workstation > (Lenovo S20). Thanks for the info! The acpiphp_bus_trim() in acpiphp_bus_add() is a leftover and a bad one. I don't think it's actually necessary, at least Thunderbolt works without it just fine on my Aspire S5. The patch below should help, can you please test it? Rafael --- From: Rafael J. Wysocki Subject: ACPI / hotplug / PCI: Don't trim devices before scanning the namespace In acpiphp_bus_add() we first remove device objects corresponding to the given handle and the ACPI namespace branch below it which are then re-created by acpi_bus_scan(). This used to be done to clean up after surprise removals, but now we do the cleanup through trim_stale_devices() which checks if the devices in question are actually gone before removing them, so the device hierarchy trimming in acpiphp_bus_add() is not necessary any more and, moreover, it may lead to problems if it removes device objects corresponding to devices that are actually present. Reported-by: Alex Williamson Signed-off-by: Rafael J. Wysocki --- drivers/pci/hotplug/acpiphp_glue.c | 1 - 1 file changed, 1 deletion(-) Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c =================================================================== --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c @@ -487,7 +487,6 @@ static void acpiphp_bus_add(acpi_handle { struct acpi_device *adev = NULL; - acpiphp_bus_trim(handle); acpi_bus_scan(handle); acpi_bus_get_device(handle, &adev); if (adev)