FAILED: patch "[PATCH] ALSA: hda: Fix hang at HD-audio codec unbinding due to" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

ead3d3c5b54f ("ALSA: hda: Fix hang at HD-audio codec unbinding due to refcount saturation") 37c4fd0db7c9 ("ALSA: hda: Do disconnect jacks at codec unbind")
7206998f578d ("ALSA: hda: Fix potential deadlock at codec unbinding")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ead3d3c5b54f76da79c079e61bacb4279ec56965 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <[email protected]>
Date: Sat, 10 Sep 2022 16:25:50 +0200
Subject: [PATCH] ALSA: hda: Fix hang at HD-audio codec unbinding due to
refcount saturation
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We fixed the potential deadlock at dynamic unbinding the HD-audio codec at the commit 7206998f578d ("ALSA: hda: Fix potential deadlock at codec unbinding"), but ironically, this caused another potential deadlock. The current code uses refcount_dec() and waits for the pending task with wait_event for dropping the refcount to 0. This works fine when PCMs are assigned and actually waiting for the refcount drop.

Meanwhile, when there was no PCM assigned, the refcount_dec() call itself was supposed to drop to zero -- alas, it doesn't in reality; refcount_dec() complains, spews kernel warning and it saturates instead of dropping to 0, due to the nature of refcount_dec() implementation. This eventually blocks the wait_event() wakeup and the code get stuck there.

For avoiding the problem, we call refcount_dec_and_test() and skips the sync-wait if it already reaches to zero.

The patch does a slight code reshuffling to make sure to invoke other disconnect calls before the sync-wait, too.

index cae9a975cbcc..1a868dd9dc4b 100644
@@ -157,10 +157,10 @@ static int hda_codec_driver_remove(struct device *dev)
 		return codec->bus->core.ext_ops->hdev_detach(&codec->core);
 	}
 
-	refcount_dec(&codec->pcm_ref);
 	snd_hda_codec_disconnect_pcms(codec);
 	snd_hda_jack_tbl_disconnect(codec);
-	wait_event(codec->remove_sleep, !refcount_read(&codec->pcm_ref));
+	if (!refcount_dec_and_test(&codec->pcm_ref))
+		wait_event(codec->remove_sleep, !refcount_read(&codec->pcm_ref));
 	snd_power_sync_ref(codec->bus->card);
 
 	if (codec->patch_ops.free)