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Date:	Fri, 31 Jan 2014 18:34:22 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [Update][PATCH 4/5][RFT] ACPI / hotplug / PCI: Simplify acpi_install_hotplug_notify_handler()

On Friday, January 31, 2014 07:09:51 PM Mika Westerberg wrote:
> On Fri, Jan 31, 2014 at 05:16:03PM +0100, Rafael J. Wysocki wrote:
> > On Friday, January 31, 2014 06:01:57 PM Mika Westerberg wrote:
> > > On Fri, Jan 31, 2014 at 05:40:11PM +0200, Mika Westerberg wrote:
> > > > On Fri, Jan 31, 2014 at 04:42:21PM +0100, Rafael J. Wysocki wrote:
> > > > > On Friday, January 31, 2014 05:28:36 PM Mika Westerberg wrote:
> > > > > > On Wed, Jan 29, 2014 at 01:00:57AM +0100, Rafael J. Wysocki wrote:
> > > > > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > > > 
> > > > > > > Use the observation that the ACPI scan handler of the device object
> > > > > > > in acpi_hotplug_notify_cb() can be obtained from that device object's
> > > > > > > handler pointer and do not pass it as data to
> > > > > > > acpi_install_hotplug_notify_handler() in acpi_scan_init_hotplug().
> > > > > > > 
> > > > > > > That allows the second argument of acpi_install_hotplug_notify_handler()
> > > > > > > to be dropped, so do it and update its callers accordingly.
> > > > > > > 
> > > > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > > > ---
> > > > > > >  drivers/acpi/scan.c                |   31 ++++++++++++++++++-------------
> > > > > > >  drivers/pci/hotplug/acpiphp_glue.c |    2 +-
> > > > > > >  include/acpi/acpi_bus.h            |    2 +-
> > > > > > >  3 files changed, 20 insertions(+), 15 deletions(-)
> > > > > > > 
> > > > > > > Index: linux-pm/drivers/acpi/scan.c
> > > > > > > ===================================================================
> > > > > > > --- linux-pm.orig/drivers/acpi/scan.c
> > > > > > > +++ linux-pm/drivers/acpi/scan.c
> > > > > > > @@ -487,7 +487,6 @@ static void acpi_device_hotplug(void *da
> > > > > > >  
> > > > > > >  static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data)
> > > > > > >  {
> > > > > > > -	struct acpi_scan_handler *handler = data;
> > > > > > >  	u32 ost_code = ACPI_OST_SC_SUCCESS;
> > > > > > >  	struct acpi_device *adev;
> > > > > > >  	acpi_status status;
> > > > > > > @@ -503,13 +502,6 @@ static void acpi_hotplug_notify_cb(acpi_
> > > > > > >  
> > > > > > >  	case ACPI_NOTIFY_EJECT_REQUEST:
> > > > > > >  		acpi_handle_debug(handle, "ACPI_NOTIFY_EJECT_REQUEST event\n");
> > > > > > > -		if (handler && !handler->hotplug.enabled) {
> > > > > > > -			acpi_handle_err(handle, "Eject disabled\n");
> > > > > > > -			ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
> > > > > > > -			goto out;
> > > > > > > -		}
> > > > > > > -		acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST,
> > > > > > > -					  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
> > > > > > >  		break;
> > > > > > >  
> > > > > > >  	case ACPI_NOTIFY_DEVICE_WAKE:
> > > > > > > @@ -535,11 +527,24 @@ static void acpi_hotplug_notify_cb(acpi_
> > > > > > >  		goto out;
> > > > > > >  	}
> > > > > > >  
> > > > > > > +	mutex_lock(&acpi_scan_lock);
> > > > > > 
> > > > > > This is weird. I'm testing against your test-next branch which has this
> > > > > > patch included. If I remove locking here, TBT hotplug works fine. Otherwise
> > > > > > I can see the first hotplug/unplug works but after that I cannot get any
> > > > > > events anymore.
> > > > > 
> > > > > Weird indeed.  I don't seem to be able to reproduce that on my Aspire S5.
> > > > > 
> > > > > What system are you testing on?
> > > > 
> > > > This is Intel NUC. Let me see if I can reproduce this on S5 with longer
> > > > chain of devices.
> > > 
> > > OK, so on S5 this works even with longer chain. However, exactly the same
> > > kernel image on NUC fails after first hotplug/unplug cycle.
> > 
> > Well, we need to figure out what happens there.
> > 
> > Please add printks (1) before mutex_lock(), (2) before the if (type == ...)
> > instruction, (3) before the acpi_evaluate_hotplug_ost() under the if () and (4)
> > before the get_device() in acpi_notify_hotplug_cb() and check if they are all
> > printed (on NUC).
> 
> Looks like something doesn't release that lock. I added printks what you
> suggested and after first hotplug/unplug last messages I get are:
> 
> [   64.914639] ACPI: \_SB_.PCI0.RP05: ACPI_NOTIFY_BUS_CHECK event
> [   64.914640] ACPI: \_SB_.PCI0.RP05: BEFORE mutex_lock()
> 
> Then running sysrq-w I get following task as blocked:
> 
> [  346.885950] SysRq : Show Blocked State
> [  346.887733]   task                        PC stack   pid father
> [  346.889535] kworker/0:0     D ffff880100241ae0  5280     4      2 0x00000000
> [  346.891355] Workqueue: kacpi_notify acpi_os_execute_deferred
> [  346.893171]  ffff8801003c7d30 0000000000000046 ffff880100241710 ffffffff81e10460
> [  346.895011]  ffff8801003c7fd8 00000000000129c0 00000000000129c0 ffff880100241710
> [  346.896849]  ffffffff81e5db70 ffffffff81e5db74 ffff880100241710 00000000ffffffff
> [  346.898702] Call Trace:
> [  346.900518]  [<ffffffff81815bc4>] schedule_preempt_disabled+0x24/0x70
> [  346.902338]  [<ffffffff818175f2>] __mutex_lock_slowpath+0x132/0x1b0
> [  346.904164]  [<ffffffff8181768a>] mutex_lock+0x1a/0x2a
> [  346.905993]  [<ffffffff81324845>] acpi_hotplug_notify_cb+0x70/0x227
> [  346.907820]  [<ffffffff813384f4>] acpi_ev_notify_dispatch+0x44/0x5c
> [  346.909637]  [<ffffffff8131fa8d>] acpi_os_execute_deferred+0xf/0x1b
> [  346.911455]  [<ffffffff8105e12a>] process_one_work+0x17a/0x440
> [  346.913285]  [<ffffffff8105ed29>] worker_thread+0x119/0x390
> [  346.915121]  [<ffffffff8105ec10>] ? manage_workers.isra.25+0x2a0/0x2a0
> [  346.916970]  [<ffffffff81064dad>] kthread+0xcd/0xf0
> [  346.918809]  [<ffffffff81064ce0>] ? kthread_create_on_node+0x180/0x180
> [  346.920653]  [<ffffffff8181fefc>] ret_from_fork+0x7c/0xb0
> [  346.922501]  [<ffffffff81064ce0>] ? kthread_create_on_node+0x180/0x180
> [  346.924351] kworker/u8:5    D ffff88006ea55860  4696   945      2 0x00000000
> [  346.926212] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> [  346.928074]  ffff88006de49a40 0000000000000046 ffff88006ea55490 ffff880100245490
> [  346.929978]  ffff88006de49fd8 00000000000129c0 00000000000129c0 ffff88006ea55490
> [  346.931872]  ffff88006de49ba0 7fffffffffffffff ffff88006de49b98 ffff88006ea55490
> [  346.933753] Call Trace:
> [  346.935626]  [<ffffffff81815794>] schedule+0x24/0x70
> [  346.937516]  [<ffffffff81814a89>] schedule_timeout+0x1a9/0x2a0
> [  346.939415]  [<ffffffff8107dda8>] ? __wake_up_common+0x58/0x90
> [  346.941312]  [<ffffffff81816968>] wait_for_completion+0x98/0x100
> [  346.943222]  [<ffffffff81071b70>] ? wake_up_state+0x10/0x10
> [  346.945133]  [<ffffffff8105ba25>] flush_workqueue+0x115/0x5a0
> [  346.947054]  [<ffffffff81309b20>] ? acpi_pci_find_companion+0x40/0x40
> [  346.948986]  [<ffffffff81309b20>] ? acpi_pci_find_companion+0x40/0x40
> [  346.950904]  [<ffffffff81320340>] acpi_os_wait_events_complete+0x1c/0x1e
> [  346.952829]  [<ffffffff8133a387>] acpi_remove_notify_handler+0x78/0x1ef
> [  346.954748]  [<ffffffff81309b20>] ? acpi_pci_find_companion+0x40/0x40
> [  346.956669]  [<ffffffff813226df>] acpi_remove_pm_notifier+0x39/0x5c
> [  346.958592]  [<ffffffff81309ab5>] pci_acpi_cleanup+0x25/0x50
> [  346.960508]  [<ffffffff8132368c>] acpi_platform_notify_remove+0x44/0x53
> [  346.962427]  [<ffffffff814426f2>] device_del+0x142/0x1b0
> [  346.964333]  [<ffffffff812edcfa>] pci_remove_bus_device+0x7a/0x100
> [  346.966238]  [<ffffffff812edd95>] pci_stop_and_remove_bus_device+0x15/0x20
> [  346.968140]  [<ffffffff8130639e>] disable_slot+0x4e/0xa0
> [  346.970030]  [<ffffffff813067b8>] acpiphp_check_bridge.part.10+0xe8/0xf0
> [  346.971911]  [<ffffffff81306f92>] hotplug_event+0xf2/0x1a0
> [  346.973776]  [<ffffffff813070a1>] acpiphp_hotplug_event+0x61/0xe0
> [  346.975630]  [<ffffffff8132634e>] acpi_device_hotplug+0x37c/0x3c2
> [  346.977471]  [<ffffffff81320359>] acpi_hotplug_work_fn+0x17/0x22
> [  346.979299]  [<ffffffff8105e12a>] process_one_work+0x17a/0x440
> [  346.981122]  [<ffffffff8105ed29>] worker_thread+0x119/0x390
> [  346.982956]  [<ffffffff8105ec10>] ? manage_workers.isra.25+0x2a0/0x2a0
> [  346.984762]  [<ffffffff81064dad>] kthread+0xcd/0xf0
> [  346.986581]  [<ffffffff81064ce0>] ? kthread_create_on_node+0x180/0x180
> [  346.988419]  [<ffffffff8181fefc>] ret_from_fork+0x7c/0xb0
> [  346.990221]  [<ffffffff81064ce0>] ? kthread_create_on_node+0x180/0x180
> 
> I have to leave now but I can continue debugging tomorrow if needed.

No need for now, I think I know what's happening.  I'll follow up later.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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