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Subject[PATCH v7 2/2] ASoC: SOF: Fix deadlock when shutdown a frozen userspace
During kexec(), the userspace might frozen. Therefore we cannot wait
for it to complete.

During a kexec with frozen processe do not unregister the clients.

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>
---
sound/soc/sof/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/soc/sof/core.c b/sound/soc/sof/core.c
index 3e6141d03770..4301f347bb90 100644
--- a/sound/soc/sof/core.c
+++ b/sound/soc/sof/core.c
@@ -9,6 +9,7 @@
//

#include <linux/firmware.h>
+#include <linux/kexec.h>
#include <linux/module.h>
#include <sound/soc.h>
#include <sound/sof.h>
@@ -484,7 +485,8 @@ int snd_sof_device_shutdown(struct device *dev)
* make sure clients and machine driver(s) are unregistered to force
* all userspace devices to be closed prior to the DSP shutdown sequence
*/
- sof_unregister_clients(sdev);
+ if (!kexec_with_frozen_processes())
+ sof_unregister_clients(sdev);

snd_sof_machine_unregister(sdev, pdata);

--
2.38.1.584.g0f3c55d4c2-goog-b4-0.11.0-dev-696ae

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