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Dell XPS 15 9550 acpi deadlock

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  Dell XPS 15 9550 acpi deadlock  Andy Clayton <clayt055@umn.edu> - 2016-02-23 23:50 +0100
    [PATCH] ACPICA: fix deadlock on recursion of entry method Andy Clayton <clayt055@umn.edu> - 2016-02-23 23:50 +0100

#1341146 — Dell XPS 15 9550 acpi deadlock

Hello,

I'm seeing a blocked acpi_os_execute_deferred task on a Dell XPS 15 9550 upon thunderbolt hotplug. It seems to prevent thunderbolt from working and causes subsequent shutdown or suspend to hang. I've put together the following patch ("ACPICA: fix deadlock on recursion of entry method") that in my testing appears to fix the issue.

Thanks for looking and for any feedback. Sorry for any gaffes as this is my first kernel patch.

Andy

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#1341150 — [PATCH] ACPICA: fix deadlock on recursion of entry method

The execution of each control method is protected by a mutex.
acpi_ds_begin_method_execution avoids trying to reacquire a mutex during
recursion by checking if the mutex is already held by the current
thread. The mutex's thread_id is only set in
acpi_ds_begin_method_execution if a walk state is present (when the
method is being called by another method). This fails for the external
entry point method executed via acpi_ps_execute_method: the mutex is
acquired but as walk_state is null the thread_id is not set. Subsequent
recursion on the entry method then blocks indefinitely attempting to
grab the mutex that the thread already holds. Fix by initializing the
mutex's thread_id with acpi_os_get_thread_id when a walk state is not
available.

For me this bug is triggered by thunderbolt hotplug on a Dell XPS 15
9550, breaking hotplug and causing subsequent suspend or shutdown to
hang indefinitely.

	INFO: task kworker/0:1:60 blocked for more than 120 seconds.
	      Not tainted 4.4.0-4-generic #19
	"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
	message.
	kworker/0:1     D ffff8804a9f13a48     0    60      2 0x00000000
	Workqueue: kacpid acpi_os_execute_deferred
	 ffff8804a9f13a48 000000000000002f 0000000000000000 ffffffff81e11540
	 ffff8804a9ea9b40 ffff8804a9f14000 ffff880378947600 ffff8804a9ea9b40
	 ffff8804ac4e26b8 ffff8804ac4e26b8 ffff8804a9f13a60 ffffffff818c38c5
	Call Trace:
	 [<ffffffff818c38c5>] schedule+0x35/0x80
	 [<ffffffff818c842e>] schedule_timeout+0x22e/0x2f0
	 [<ffffffff810214f9>] ? sched_clock+0x9/0x10
	 [<ffffffff810b97ac>] ? local_clock+0x1c/0x20
	 [<ffffffff810da359>] ? mark_held_locks+0x79/0xa0
	 [<ffffffff818c941c>] ? _raw_spin_unlock_irq+0x2c/0x40
	 [<ffffffff810da4a9>] ? trace_hardirqs_on_caller+0x129/0x1b0
	 [<ffffffff818c7304>] __down_timeout+0x74/0xd0
	 [<ffffffff810d4169>] ? down_timeout+0x19/0x60
	 [<ffffffff810d419c>] down_timeout+0x4c/0x60
	 [<ffffffff814c646c>] acpi_os_wait_semaphore+0xaa/0x16c
	 [<ffffffff814f37b9>] acpi_ex_system_wait_mutex+0x81/0xfa
	 [<ffffffff814daefc>] acpi_ds_begin_method_execution+0x25e/0x378
	 [<ffffffff814db460>] acpi_ds_call_control_method+0x107/0x2de
	 [<ffffffff8150112f>] acpi_ps_parse_aml+0x17e/0x493
	 [<ffffffff81501e14>] acpi_ps_execute_method+0x1fa/0x2ba
	 [<ffffffff814f90fa>] acpi_ns_evaluate+0x2e6/0x42d
	 [<ffffffff814e203b>] acpi_ev_asynch_execute_gpe_method+0xbd/0x159
	 [<ffffffff814c55b0>] acpi_os_execute_deferred+0x14/0x20
	 [<ffffffff8109f93e>] process_one_work+0x1ee/0x570
	 [<ffffffff8109f8d2>] ? process_one_work+0x182/0x570
	 [<ffffffff8109fd08>] worker_thread+0x48/0x4a0
	 [<ffffffff8109fcc0>] ? process_one_work+0x570/0x570
	 [<ffffffff810a6456>] kthread+0xf6/0x110
	 [<ffffffff810da4a9>] ? trace_hardirqs_on_caller+0x129/0x1b0
	 [<ffffffff810a6360>] ? kthread_create_on_node+0x290/0x290
	 [<ffffffff818ca16f>] ret_from_fork+0x3f/0x70
	 [<ffffffff810a6360>] ? kthread_create_on_node+0x290/0x290

And part of the impacted method from the DSDT:

        Method (_E42, 0, NotSerialized)  // _Exx: Edge-Triggered GPE
        {
            (...)

            ADBG ("TBT-HP-Handler")
            ADBG ("PEG WorkAround")
            PGWA ()
            Acquire (OSUM, 0xFFFF)
            Local1 = TBFF ()
            If ((Local1 == One))
            {
                Sleep (0x10)
                Release (OSUM)
                ADBG ("OS_Up_Received")
                If (((DPTF == One) && (DDDR == One)))
                {
                    If (((OSYS == 0x07DD) && (_REV == 0x05)))
                    {
                        Return (Zero)
                    }

                    _E42 ()
                }

                Return (Zero)
            }

            (...)
        }

Signed-off-by: Andy Clayton <clayt055@umn.edu>
---
 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 6a72047..c3a052d 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();
 			}
 		}
 
-- 
2.7.0

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