[PATCH] ASoC: soc-compress: Reposition and add pcm_mutex

[강신형]

If panic_on_warn is set and compress stream(DPCM) is started,
then kernel panic occurred because card->pcm_mutex isn't held appropriately.
In the following functions, warning were issued at this line
"snd_soc_dpcm_mutex_assert_held".

static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
		struct snd_soc_pcm_runtime *be, int stream)
{
	...
	snd_soc_dpcm_mutex_assert_held(fe);
	...
}

void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
{
	...
	snd_soc_dpcm_mutex_assert_held(fe);
	...
}

void snd_soc_runtime_action(struct snd_soc_pcm_runtime *rtd,
			    int stream, int action)
{
	...
	snd_soc_dpcm_mutex_assert_held(rtd);
	...
}

int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
	int event)
{
	...
	snd_soc_dpcm_mutex_assert_held(fe);
	...
}

These functions are called by soc_compr_set_params_fe, soc_compr_open_fe
and soc_compr_free_fe
without pcm_mutex locking. And this is call stack.

[  414.527841][ T2179] pc : dpcm_process_paths+0x5a4/0x750
[  414.527848][ T2179] lr : dpcm_process_paths+0x37c/0x750
[  414.527945][ T2179] Call trace:
[  414.527949][ T2179]  dpcm_process_paths+0x5a4/0x750
[  414.527955][ T2179]  soc_compr_open_fe+0xb0/0x2cc
[  414.527972][ T2179]  snd_compr_open+0x180/0x248
[  414.527981][ T2179]  snd_open+0x15c/0x194
[  414.528003][ T2179]  chrdev_open+0x1b0/0x220
[  414.528023][ T2179]  do_dentry_open+0x30c/0x594
[  414.528045][ T2179]  vfs_open+0x34/0x44
[  414.528053][ T2179]  path_openat+0x914/0xb08
[  414.528062][ T2179]  do_filp_open+0xc0/0x170
[  414.528068][ T2179]  do_sys_openat2+0x94/0x18c
[  414.528076][ T2179]  __arm64_sys_openat+0x78/0xa4
[  414.528084][ T2179]  invoke_syscall+0x48/0x10c
[  414.528094][ T2179]  el0_svc_common+0xbc/0x104
[  414.528099][ T2179]  do_el0_svc+0x34/0xd8
[  414.528103][ T2179]  el0_svc+0x34/0xc4
[  414.528125][ T2179]  el0t_64_sync_handler+0x8c/0xfc
[  414.528133][ T2179]  el0t_64_sync+0x1a0/0x1a4
[  414.528142][ T2179] Kernel panic - not syncing: panic_on_warn set ...

So, I reposition and add pcm_mutex to resolve lockdep error.

Signed-off-by: Shinhyung Kang <s47.kang at samsung.com>
---
 sound/soc/soc-compress.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
index 870f13e1d389..7bce5088b455 100644
--- a/sound/soc/soc-compress.c
+++ b/sound/soc/soc-compress.c
@@ -149,6 +149,8 @@ static int soc_compr_open_fe(struct snd_compr_stream
*cstream)
 	if (ret < 0)
 		goto be_err;
 
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
+
 	/* calculate valid and active FE <-> BE dpcms */
 	dpcm_process_paths(fe, stream, &list, 1);
 	fe->dpcm[stream].runtime = fe_substream->runtime;
@@ -184,7 +186,6 @@ 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);
 
@@ -215,7 +216,6 @@ static int soc_compr_free_fe(struct snd_compr_stream
*cstream)
 
 	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;
 
@@ -234,6 +234,8 @@ static int soc_compr_free_fe(struct snd_compr_stream
*cstream)
 
 	dpcm_be_disconnect(fe, stream);
 
+	mutex_unlock(&fe->card->pcm_mutex);
+
 	fe->dpcm[stream].runtime = NULL;
 
 	snd_soc_link_compr_shutdown(cstream, 0);
@@ -409,8 +411,9 @@ static int soc_compr_set_params_fe(struct
snd_compr_stream *cstream,
 	ret = snd_soc_link_compr_set_params(cstream);
 	if (ret < 0)
 		goto out;
-
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
 	dpcm_dapm_stream_event(fe, stream, SND_SOC_DAPM_STREAM_START);
+	mutex_unlock(&fe->card->pcm_mutex);
 	fe->dpcm[stream].state = SND_SOC_DPCM_STATE_PREPARE;
 
 out:
-- 
2.21.0