FAILED: patch "[PATCH] ALSA: jack: Fix mutex call in snd_jack_report()" 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]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 89dbb335cb6a627a4067bc42caa09c8bc3326d40
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023071156-amicably-trowel-5ddf@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 89dbb335cb6a627a4067bc42caa09c8bc3326d40 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <[email protected]>
Date: Thu, 6 Jul 2023 17:53:57 +0200
Subject: [PATCH] ALSA: jack: Fix mutex call in snd_jack_report()
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snd_jack_report() is supposed to be callable from an IRQ context, too, and it's indeed used in that way from virtsnd driver. The fix for input_dev race in commit 1b6a6fc5280e ("ALSA: jack: Access input_dev under mutex"), however, introduced a mutex lock in snd_jack_report(), and this resulted in a potential sleep-in-atomic.

For addressing that problem, this patch changes the relevant code to use the object get/put and removes the mutex usage. That is, snd_jack_report(), it takes input_get_device() and leaves with input_put_device() for assuring the input_dev being assigned.

Although the whole mutex could be reduced, we keep it because it can be still a protection for potential races between creation and deletion.

index 88493cc31914..03d155ed362b 100644
@@ -654,6 +654,7 @@ void snd_jack_report(struct snd_jack *jack, int status)
 	struct snd_jack_kctl *jack_kctl;
 	unsigned int mask_bits = 0;
 #ifdef CONFIG_SND_JACK_INPUT_DEV
+	struct input_dev *idev;
 	int i;
 #endif
 

@@ -670,17 +671,15 @@ void snd_jack_report(struct snd_jack *jack, int status)
 					     status & jack_kctl->mask_bits);
 
 #ifdef CONFIG_SND_JACK_INPUT_DEV
-	mutex_lock(&jack->input_dev_lock);
-	if (!jack->input_dev) {
-		mutex_unlock(&jack->input_dev_lock);
+	idev = input_get_device(jack->input_dev);
+	if (!idev)
 		return;
-	}
 
 	for (i = 0; i < ARRAY_SIZE(jack->key); i++) {
 		int testbit = ((SND_JACK_BTN_0 >> i) & ~mask_bits);
 
 		if (jack->type & testbit)
-			input_report_key(jack->input_dev, jack->key[i],
+			input_report_key(idev, jack->key[i],
 					 status & testbit);
 	}
 

@@ -688,13 +687,13 @@ void snd_jack_report(struct snd_jack *jack, int status)
 		int testbit = ((1 << i) & ~mask_bits);
 
 		if (jack->type & testbit)
-			input_report_switch(jack->input_dev,
+			input_report_switch(idev,
 					    jack_switch_types[i],
 					    status & testbit);
 	}
 
-	input_sync(jack->input_dev);
-	mutex_unlock(&jack->input_dev_lock);
+	input_sync(idev);
+	input_put_device(idev);
 #endif /* CONFIG_SND_JACK_INPUT_DEV */
 }
 EXPORT_SYMBOL(snd_jack_report);