[PATCH v4] ALSA: core: Fix deadlock when shutdown a frozen userspace

[Ricardo Ribalda <ribalda@chromium.org>]

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@vger.kernel.org
Fixes: 83bfc7e793b5 ("ASoC: SOF: core: unregister clients and machine drivers in .shutdown")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
To: Liam Girdwood <lgirdwood@gmail.com>
To: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
To: Bard Liao <yung-chuan.liao@linux.intel.com>
To: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
To: Kai Vehmanen <kai.vehmanen@linux.intel.com>
To: Daniel Baluta <daniel.baluta@nxp.com>
To: Mark Brown <broonie@kernel.org>
To: Jaroslav Kysela <perex@perex.cz>
To: Takashi Iwai <tiwai@suse.com>
Cc: sound-open-firmware@alsa-project.org
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.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);
-
 	if (sdev->fw_state == SOF_FW_BOOT_COMPLETE)
 		return snd_sof_shutdown(sdev);
 

---
base-commit: 4312098baf37ee17a8350725e6e0d0e8590252d4
change-id: 20221127-snd-freeze-1ee143228326

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>