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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Gyeongtaek Lee <gt82.lee@samsung.com>,
        Mark Brown <broonie@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.11 055/329] ASoC: soc-compress: lock pcm_mutex to resolve lockdep error
Date:   Mon, 17 May 2021 15:59:26 +0200
Message-Id: <20210517140303.925001407@linuxfoundation.org>
In-Reply-To: <20210517140302.043055203@linuxfoundation.org>
References: <20210517140302.043055203@linuxfoundation.org>
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From: Gyeongtaek Lee <gt82.lee@samsung.com>

[ Upstream commit 45475bf60cc1d42da229a0aa757180c88bab8d22 ]

If panic_on_warn=1 is added in bootargs and compress offload playback with
DPCM is started, kernel panic would be occurred because rtd->card->pcm_mutex
isn't held in soc_compr_open_fe() and soc_compr_free_fe() and it generates
lockdep warning in the following code.

void snd_soc_runtime_action(struct snd_soc_pcm_runtime *rtd,
			    int stream, int action)
{
	struct snd_soc_dai *dai;
	int i;

	lockdep_assert_held(&rtd->card->pcm_mutex);

To prevent lockdep warning but minimize side effect by adding mutex,
pcm_mutex is held just before snd_soc_runtime_activate() and
snd_soc_runtime_deactivate() and is released right after them.

Signed-off-by: Gyeongtaek Lee <gt82.lee@samsung.com>
Link: https://lore.kernel.org/r/1891546521.01617772502282.JavaMail.epsvc@epcpadp3
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/soc/soc-compress.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
index 246a5e32e22a..b4810266f5e5 100644
--- a/sound/soc/soc-compress.c
+++ b/sound/soc/soc-compress.c
@@ -153,7 +153,9 @@ static int soc_compr_open_fe(struct snd_compr_stream *cstream)
 	fe->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
 	fe->dpcm[stream].runtime_update = SND_SOC_DPCM_UPDATE_NO;
 
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
 	snd_soc_runtime_activate(fe, stream);
+	mutex_unlock(&fe->card->pcm_mutex);
 
 	mutex_unlock(&fe->card->mutex);
 
@@ -181,7 +183,9 @@ static int soc_compr_free_fe(struct snd_compr_stream *cstream)
 
 	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
 
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
 	snd_soc_runtime_deactivate(fe, stream);
+	mutex_unlock(&fe->card->pcm_mutex);
 
 	fe->dpcm[stream].runtime_update = SND_SOC_DPCM_UPDATE_FE;
 
-- 
2.30.2