[PATCH 2/2] ASoC: max98090: fix lockdep warning
From: Marek Szyprowski
Date: Wed Jan 08 2020 - 06:50:33 EST
Commit 62d5ae4cafb7 ("ASoC: max98090: save and restore SHDN when changing
sensitive registers") extended the code for handling many controls by
adding a custom put function to them. That new custom put function
properly handles relations between codec's hardware registers. However
they used card->dapm_mutex to properly serialize those operations. This
in turn triggers a lockdep warning about possible circular dependency.
Fix this by introducing a separate mutex only for serializing the SHDN
hardware register related operations.
This fixes the following lockdep warning observed on Exynos4412-based
Odroid U3 board:
======================================================
WARNING: possible circular locking dependency detected
5.5.0-rc5-next-20200107 #166 Not tainted
------------------------------------------------------
alsactl/1104 is trying to acquire lock:
ed0d50f4 (&card->dapm_mutex){+.+.}, at: max98090_shdn_save+0x1c/0x28
but task is already holding lock:
edb4b49c (&card->controls_rwsem){++++}, at: snd_ctl_ioctl+0xcc/0xbb8
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&card->controls_rwsem){++++}:
snd_ctl_add_replace+0x3c/0x84
dapm_create_or_share_kcontrol+0x24c/0x2e0
snd_soc_dapm_new_widgets+0x308/0x594
snd_soc_bind_card+0x80c/0xad4
devm_snd_soc_register_card+0x34/0x6c
odroid_audio_probe+0x288/0x34c
platform_drv_probe+0x6c/0xa4
really_probe+0x200/0x490
driver_probe_device+0x78/0x1f8
bus_for_each_drv+0x74/0xb8
__device_attach+0xd4/0x16c
bus_probe_device+0x88/0x90
deferred_probe_work_func+0x3c/0xd0
process_one_work+0x22c/0x7c4
worker_thread+0x44/0x524
kthread+0x130/0x164
ret_from_fork+0x14/0x20
0x0
-> #0 (&card->dapm_mutex){+.+.}:
lock_acquire+0xe8/0x270
__mutex_lock+0x9c/0xb18
mutex_lock_nested+0x1c/0x24
max98090_shdn_save+0x1c/0x28
max98090_put_enum_double+0x20/0x40
snd_ctl_ioctl+0x190/0xbb8
ksys_ioctl+0x470/0xaf8
ret_fast_syscall+0x0/0x28
0xbefaa564
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&card->controls_rwsem);
lock(&card->dapm_mutex);
lock(&card->controls_rwsem);
lock(&card->dapm_mutex);
*** DEADLOCK ***
1 lock held by alsactl/1104:
#0: edb4b49c (&card->controls_rwsem){++++}, at: snd_ctl_ioctl+0xcc/0xbb8
stack backtrace:
CPU: 0 PID: 1104 Comm: alsactl Not tainted 5.5.0-rc5-next-20200107 #166
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
(unwind_backtrace) from [<c010e180>] (show_stack+0x10/0x14)
(show_stack) from [<c0b2a09c>] (dump_stack+0xb4/0xe0)
(dump_stack) from [<c018a1c0>] (check_noncircular+0x1ec/0x208)
(check_noncircular) from [<c018c5dc>] (__lock_acquire+0x1210/0x25ec)
(__lock_acquire) from [<c018e2d8>] (lock_acquire+0xe8/0x270)
(lock_acquire) from [<c0b49678>] (__mutex_lock+0x9c/0xb18)
(__mutex_lock) from [<c0b4a110>] (mutex_lock_nested+0x1c/0x24)
(mutex_lock_nested) from [<c0839b3c>] (max98090_shdn_save+0x1c/0x28)
(max98090_shdn_save) from [<c083a5b8>] (max98090_put_enum_double+0x20/0x40)
(max98090_put_enum_double) from [<c080d0e8>] (snd_ctl_ioctl+0x190/0xbb8)
(snd_ctl_ioctl) from [<c02cafec>] (ksys_ioctl+0x470/0xaf8)
(ksys_ioctl) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
...
Fixes: 62d5ae4cafb7 ("ASoC: max98090: save and restore SHDN when changing sensitive registers")
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
sound/soc/codecs/max98090.c | 10 ++++++----
sound/soc/codecs/max98090.h | 1 +
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index c01ce4a3f86d..454cb8e5b0a1 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -52,14 +52,14 @@ static void max98090_shdn_restore_locked(struct max98090_priv *max98090)
static void max98090_shdn_save(struct max98090_priv *max98090)
{
- mutex_lock(&max98090->component->card->dapm_mutex);
+ mutex_lock(&max98090->shdn_lock);
max98090_shdn_save_locked(max98090);
}
static void max98090_shdn_restore(struct max98090_priv *max98090)
{
max98090_shdn_restore_locked(max98090);
- mutex_unlock(&max98090->component->card->dapm_mutex);
+ mutex_unlock(&max98090->shdn_lock);
}
static int max98090_put_volsw(struct snd_kcontrol *kcontrol,
@@ -2313,12 +2313,12 @@ static void max98090_pll_work(struct max98090_priv *max98090)
*/
/* Toggle shutdown OFF then ON */
- mutex_lock(&component->card->dapm_mutex);
+ mutex_lock(&max98090->shdn_lock);
snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
M98090_SHDNN_MASK, 0);
snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
M98090_SHDNN_MASK, M98090_SHDNN_MASK);
- mutex_unlock(&component->card->dapm_mutex);
+ mutex_unlock(&max98090->shdn_lock);
for (i = 0; i < 10; ++i) {
/* Give PLL time to lock */
@@ -2731,6 +2731,8 @@ static int max98090_i2c_probe(struct i2c_client *i2c,
if (max98090 == NULL)
return -ENOMEM;
+ mutex_init(&max98090->shdn_lock);
+
if (ACPI_HANDLE(&i2c->dev)) {
acpi_id = acpi_match_device(i2c->dev.driver->acpi_match_table,
&i2c->dev);
diff --git a/sound/soc/codecs/max98090.h b/sound/soc/codecs/max98090.h
index 0a31708b7df7..dabd8be34a01 100644
--- a/sound/soc/codecs/max98090.h
+++ b/sound/soc/codecs/max98090.h
@@ -1539,6 +1539,7 @@ struct max98090_priv {
unsigned int pa2en;
unsigned int sidetone;
bool master;
+ struct mutex shdn_lock;
int saved_count;
int saved_shdn;
};
--
2.17.1