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Date: Fri, 15 Apr 2016 10:39:50 +0300
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Prarit Bhargava <prarit@redhat.com>
Cc: linux-kernel@vger.kernel.org, Robert Moore <robert.moore@intel.com>,
        Lv Zheng <lv.zheng@intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Len Brown <lenb@kernel.org>, linux-acpi@vger.kernel.org,
        devel@acpica.org
Subject: Re: [PATCH] acpi/acpica: fix Thunderbolt hotplug
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Bob, Rafael, any comments about this?

This seems to solve a real issue with Thunderbolt hotplug on Dell XPS
laptops. I do not know ACPICA that well to tell if this is 100% correct
fix but many reporters say it fixes the problem they are facing:

https://bugzilla.kernel.org/show_bug.cgi?id=115121

On Tue, Mar 29, 2016 at 06:45:40PM -0400, Prarit Bhargava wrote:
> The following hung task trace is seen when hotplugging
> an ethernet dongle in a Thunderbolt port on Linux.
> 
> INFO: task kworker/0:4:1468 blocked for more than 120 seconds.
>       Tainted: G        W       4.6.0-rc1+ #1
>  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>  kworker/0:4     D ffff8802a265ba38 13344  1468      2 0x00000000
>  Workqueue: kacpid acpi_os_execute_deferred
>  ffff8802a265ba38 ffff8802a265ba00 ffffffff81130200 ffffffff81e0d580
>  ffff88029e5eb340 ffff8802a265c000 ffff88029d69d000 ffff88029e5eb340
>  ffffffff818c1b8d ffff8802b64e8758 ffff8802a265ba50 ffffffff818bdfcc
>  Call Trace:
>  [<ffffffff81130200>] ? test_callback+0x10/0x30
>  [<ffffffff818c1b8d>] ? __down_timeout+0x5d/0xd0
>  [<ffffffff818bdfcc>] schedule+0x3c/0x90
>  [<ffffffff818c2d60>] schedule_timeout+0x210/0x360
>  [<ffffffff8103fc89>] ? sched_clock+0x9/0x10
>  [<ffffffff810ee51c>] ? local_clock+0x1c/0x20
>  [<ffffffff81110c16>] ? mark_held_locks+0x76/0xa0
>  [<ffffffff818c3cfc>] ? _raw_spin_unlock_irq+0x2c/0x40
>  [<ffffffff818c1b8d>] ? __down_timeout+0x5d/0xd0
>  [<ffffffff81110d35>] ? trace_hardirqs_on_caller+0xf5/0x1b0
>  [<ffffffff818c1b8d>] ? __down_timeout+0x5d/0xd0
>  [<ffffffff818c1bac>] __down_timeout+0x7c/0xd0
>  [<ffffffff818c44b2>] ? _raw_spin_lock_irqsave+0x82/0x90
>  [<ffffffff8110b87c>] down_timeout+0x4c/0x60
>  [<ffffffff814e3a9c>] acpi_os_wait_semaphore+0xaa/0x16a
>  [<ffffffff81510f37>] acpi_ex_system_wait_mutex+0x81/0xfa
>  [<ffffffff814f8796>] acpi_ds_begin_method_execution+0x25a/0x373
>  [<ffffffff814f8cea>] acpi_ds_call_control_method+0x107/0x2e0
>  [<ffffffff8151ed60>] acpi_ps_parse_aml+0x177/0x495
>  [<ffffffff8151fa46>] acpi_ps_execute_method+0x1f7/0x2b9
>  [<ffffffff81516c9a>] acpi_ns_evaluate+0x2ee/0x435
>  [<ffffffff814ff84a>] acpi_ev_asynch_execute_gpe_method+0xbd/0x159
>  [<ffffffff814e2a69>] acpi_os_execute_deferred+0x17/0x23
>  [<ffffffff810d1fc2>] process_one_work+0x242/0x700
>  [<ffffffff810d1f3a>] ? process_one_work+0x1ba/0x700
>  [<ffffffff810d24ce>] worker_thread+0x4e/0x490
>  [<ffffffff810d2480>] ? process_one_work+0x700/0x700
>  [<ffffffff810d2480>] ? process_one_work+0x700/0x700
>  [<ffffffff810d98b1>] kthread+0x101/0x120
>  [<ffffffff81110d35>] ? trace_hardirqs_on_caller+0xf5/0x1b0
>  [<ffffffff818c4832>] ret_from_fork+0x22/0x50
>  [<ffffffff810d97b0>] ? kthread_create_on_node+0x250/0x250
>  2 locks held by kworker/0:4/1468:
>  #0:  ("kacpid"){.+.+.+}, at: [<ffffffff810d1f3a>] process_one_work+0x1ba/0x700
>  #1:  ((&dpc->work)){+.+.+.}, at: [<ffffffff810d1f3a>] process_one_work+0x1ba/0x700
> 
> The issue appears to be that the kworker thread attempts to acquire the
> _E42 method's mutex twice when executing  acpi_ps_execute_method() and
> recursing through the entry method.
> 
> The current code does take the possiblity of this recursion into account,
> however, it is only for the case where the walk_state has been populated.
> 
> This can be fixed by setting the thread id in the !walk_state case to
> allow for recursion.
> 
> Cc: Robert Moore <robert.moore@intel.com>
> Cc: Lv Zheng <lv.zheng@intel.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: linux-acpi@vger.kernel.org
> Cc: devel@acpica.org
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> ---
>  drivers/acpi/acpica/dsmethod.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/acpica/dsmethod.c b/drivers/acpi/acpica/dsmethod.c
> index 1982310..93799db 100644
> --- a/drivers/acpi/acpica/dsmethod.c
> +++ b/drivers/acpi/acpica/dsmethod.c
> @@ -428,6 +428,9 @@ acpi_ds_begin_method_execution(struct acpi_namespace_node *method_node,
>  				obj_desc->method.mutex->mutex.
>  				    original_sync_level =
>  				    obj_desc->method.mutex->mutex.sync_level;
> +
> +				obj_desc->method.mutex->mutex.thread_id =
> +					acpi_os_get_thread_id();
>  			}
>  		}
>  
> -- 
> 1.7.9.3
> 
> --
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