RE: [PATCH] acpi/acpica: fix Thunderbolt hotplug

["Moore, Robert" <robert.moore@intel.com>]

Lv is looking at it. He has already commented that this might not be the best solution, so he is continuing to investigate.


> -----Original Message-----
> From: Mika Westerberg [mailto:mika.westerberg@linux.intel.com]
> Sent: Friday, April 15, 2016 12:40 AM
> To: Prarit Bhargava
> Cc: linux-kernel@vger.kernel.org; Moore, Robert; Zheng, Lv; Wysocki,
> Rafael J; Len Brown; linux-acpi@vger.kernel.org; devel@acpica.org
> Subject: Re: [PATCH] acpi/acpica: fix Thunderbolt hotplug
> 
> 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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