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Message-ID: <16ddcbb9-8afa-ff18-05f9-2e9e01baf3ea@linux.intel.com>
Date: Mon, 28 Nov 2022 11:26:03 -0600
From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: alsa-devel@...a-project.org,
Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
Liam Girdwood <lgirdwood@...il.com>,
Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
Takashi Iwai <tiwai@...e.com>, stable@...r.kernel.org,
Mark Brown <broonie@...nel.org>,
Bard Liao <yung-chuan.liao@...ux.intel.com>,
Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
Ricardo Ribalda <ribalda@...omium.org>,
Daniel Baluta <daniel.baluta@....com>,
linux-kernel@...r.kernel.org, sound-open-firmware@...a-project.org
Subject: Re: [PATCH v4] ALSA: core: Fix deadlock when shutdown a frozen
userspace
On 11/28/22 11:04, Takashi Iwai wrote:
> On Mon, 28 Nov 2022 17:49:20 +0100,
> Pierre-Louis Bossart wrote:
>>
>>
>>
>> On 11/28/22 07:42, Ricardo Ribalda wrote:
>>> During kexec(), the userspace is frozen. Therefore we cannot wait for it
>>> to complete.
>>>
>>> Avoid running snd_sof_machine_unregister during shutdown.
>>>
>>> This fixes:
>>>
>>> [ 84.943749] Freezing user space processes ... (elapsed 0.111 seconds) done.
>>> [ 246.784446] INFO: task kexec-lite:5123 blocked for more than 122 seconds.
>>> [ 246.819035] Call Trace:
>>> [ 246.821782] <TASK>
>>> [ 246.824186] __schedule+0x5f9/0x1263
>>> [ 246.828231] schedule+0x87/0xc5
>>> [ 246.831779] snd_card_disconnect_sync+0xb5/0x127
>>> ...
>>> [ 246.889249] snd_sof_device_shutdown+0xb4/0x150
>>> [ 246.899317] pci_device_shutdown+0x37/0x61
>>> [ 246.903990] device_shutdown+0x14c/0x1d6
>>> [ 246.908391] kernel_kexec+0x45/0xb9
>>>
>>> And:
>>>
>>> [ 246.893222] INFO: task kexec-lite:4891 blocked for more than 122 seconds.
>>> [ 246.927709] Call Trace:
>>> [ 246.930461] <TASK>
>>> [ 246.932819] __schedule+0x5f9/0x1263
>>> [ 246.936855] ? fsnotify_grab_connector+0x5c/0x70
>>> [ 246.942045] schedule+0x87/0xc5
>>> [ 246.945567] schedule_timeout+0x49/0xf3
>>> [ 246.949877] wait_for_completion+0x86/0xe8
>>> [ 246.954463] snd_card_free+0x68/0x89
>>> ...
>>> [ 247.001080] platform_device_unregister+0x12/0x35
>>>
>>> Cc: stable@...r.kernel.org
>>> Fixes: 83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers in .shutdown")
>>> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>>> ---
>>> To: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
>>> To: Liam Girdwood <lgirdwood@...il.com>
>>> To: Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>
>>> To: Bard Liao <yung-chuan.liao@...ux.intel.com>
>>> To: Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>
>>> To: Kai Vehmanen <kai.vehmanen@...ux.intel.com>
>>> To: Daniel Baluta <daniel.baluta@....com>
>>> To: Mark Brown <broonie@...nel.org>
>>> To: Jaroslav Kysela <perex@...ex.cz>
>>> To: Takashi Iwai <tiwai@...e.com>
>>> Cc: sound-open-firmware@...a-project.org
>>> Cc: alsa-devel@...a-project.org
>>> Cc: linux-kernel@...r.kernel.org
>>> ---
>>> Changes in v4:
>>> - Do not call snd_sof_machine_unregister from shutdown.
>>> - Link to v3: https://lore.kernel.org/r/20221127-snd-freeze-v3-0-a2eda731ca14@chromium.org
>>>
>>> Changes in v3:
>>> - Wrap pm_freezing in a function
>>> - Link to v2: https://lore.kernel.org/r/20221127-snd-freeze-v2-0-d8a425ea9663@chromium.org
>>>
>>> Changes in v2:
>>> - Only use pm_freezing if CONFIG_FREEZER
>>> - Link to v1: https://lore.kernel.org/r/20221127-snd-freeze-v1-0-57461a366ec2@chromium.org
>>> ---
>>> sound/soc/sof/core.c | 7 ++-----
>>> 1 file changed, 2 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/sound/soc/sof/core.c b/sound/soc/sof/core.c
>>> index 3e6141d03770..9616ba607ded 100644
>>> --- a/sound/soc/sof/core.c
>>> +++ b/sound/soc/sof/core.c
>>> @@ -475,19 +475,16 @@ EXPORT_SYMBOL(snd_sof_device_remove);
>>> int snd_sof_device_shutdown(struct device *dev)
>>> {
>>> struct snd_sof_dev *sdev = dev_get_drvdata(dev);
>>> - struct snd_sof_pdata *pdata = sdev->pdata;
>>>
>>> if (IS_ENABLED(CONFIG_SND_SOC_SOF_PROBE_WORK_QUEUE))
>>> cancel_work_sync(&sdev->probe_work);
>>>
>>> /*
>>> - * make sure clients and machine driver(s) are unregistered to force
>>> - * all userspace devices to be closed prior to the DSP shutdown sequence
>>> + * make sure clients are unregistered prior to the DSP shutdown
>>> + * sequence.
>>> */
>>> sof_unregister_clients(sdev);
>>>
>>> - snd_sof_machine_unregister(sdev, pdata);
>>> -
>>
>> The comment clearly says that we do want all userspace devices to be
>> closed. This was added in 83bfc7e793b5 ("ASoC: SOF: core: unregister
>> clients and machine drivers in .shutdown") precisely to avoid a platform
>> hang if the devices are used after the shutdown completes.
>
> The problem is that it wants the *close* of the user-space programs
> unnecessarily. Basically the shutdown can be seen as a sort of device
> hot unplug; i.e. the disconnection of the device files and the cleanup
> of device state are the main task. The difference is that the hot
> unplug (unbind) usually follows the sync for the all processes being
> closed (so that you can release all resources gracefully), while this
> step is skipped for the shutdown (no need for resource-free).
Sorry Takashi, I don't have enough background to follow your explanations.
As Kai mentioned it, this step helped with a S5 issue earlier in 2022.
Removing this will mechanically bring the issue back and break other
Chromebooks.
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