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Message-ID: <2014200.ZMkXkiESpH@vostro.rjw.lan> Date: Sun, 02 Feb 2014 01:12 +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 06:34:22 PM Rafael J. Wysocki wrote: > 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: [...] > > > > [ 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. acpi_remove_notify_handler() which is called from acpi_remove_pm_notifier() executes acpi_os_wait_events_complete() which does flush_workqueue(kacpi_notify_wq) and all that happens under acpi_scan_lock acquired by acpi_device_hotplug(). Now, acpi_hotplug_notify_cb() runs from kacpi_notify_wq, so effectively acpi_os_wait_events_complete() waits for it to return, so if it attempts to acquire acpi_scan_lock, it will deadlock. Which happens on the NUC. The good news is that we can use a different lock to eliminate the race I wanted to deal with using acpi_scan_lock, but that required me to rework the whole patchset. I'll send a new version shortly, but I need to update the ACPIPHP updates it is on top of. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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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