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Subject[PATCH 3.18 33/39] ALSA: ak411x: Fix stall in work callback
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 4161b4505f1690358ac0a9ee59845a7887336b21 upstream.

When ak4114 work calls its callback and the callback invokes
ak4114_reinit(), it stalls due to flush_delayed_work(). For avoiding
this, control the reentrance by introducing a refcount. Also
flush_delayed_work() is replaced with cancel_delayed_work_sync().

The exactly same bug is present in ak4113.c and fixed as well.

Reported-by: Pavel Hofman <pavel.hofman@ivitera.com>
Acked-by: Jaroslav Kysela <perex@perex.cz>
Tested-by: Pavel Hofman <pavel.hofman@ivitera.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/sound/ak4113.h | 2 +-
include/sound/ak4114.h | 2 +-
sound/i2c/other/ak4113.c | 17 ++++++++---------
sound/i2c/other/ak4114.c | 18 ++++++++----------
4 files changed, 18 insertions(+), 21 deletions(-)

--- a/include/sound/ak4113.h
+++ b/include/sound/ak4113.h
@@ -286,7 +286,7 @@ struct ak4113 {
ak4113_write_t *write;
ak4113_read_t *read;
void *private_data;
- unsigned int init:1;
+ atomic_t wq_processing;
spinlock_t lock;
unsigned char regmap[AK4113_WRITABLE_REGS];
struct snd_kcontrol *kctls[AK4113_CONTROLS];
--- a/include/sound/ak4114.h
+++ b/include/sound/ak4114.h
@@ -168,7 +168,7 @@ struct ak4114 {
ak4114_write_t * write;
ak4114_read_t * read;
void * private_data;
- unsigned int init: 1;
+ atomic_t wq_processing;
spinlock_t lock;
unsigned char regmap[6];
unsigned char txcsb[5];
--- a/sound/i2c/other/ak4113.c
+++ b/sound/i2c/other/ak4113.c
@@ -56,8 +56,7 @@ static inline unsigned char reg_read(str

static void snd_ak4113_free(struct ak4113 *chip)
{
- chip->init = 1; /* don't schedule new work */
- mb();
+ atomic_inc(&chip->wq_processing); /* don't schedule new work */
cancel_delayed_work_sync(&chip->work);
kfree(chip);
}
@@ -89,6 +88,7 @@ int snd_ak4113_create(struct snd_card *c
chip->write = write;
chip->private_data = private_data;
INIT_DELAYED_WORK(&chip->work, ak4113_stats);
+ atomic_set(&chip->wq_processing, 0);

for (reg = 0; reg < AK4113_WRITABLE_REGS ; reg++)
chip->regmap[reg] = pgm[reg];
@@ -139,13 +139,11 @@ static void ak4113_init_regs(struct ak41

void snd_ak4113_reinit(struct ak4113 *chip)
{
- chip->init = 1;
- mb();
- flush_delayed_work(&chip->work);
+ if (atomic_inc_return(&chip->wq_processing) == 1)
+ cancel_delayed_work_sync(&chip->work);
ak4113_init_regs(chip);
/* bring up statistics / event queing */
- chip->init = 0;
- if (chip->kctls[0])
+ if (atomic_dec_and_test(&chip->wq_processing))
schedule_delayed_work(&chip->work, HZ / 10);
}
EXPORT_SYMBOL_GPL(snd_ak4113_reinit);
@@ -632,8 +630,9 @@ static void ak4113_stats(struct work_str
{
struct ak4113 *chip = container_of(work, struct ak4113, work.work);

- if (!chip->init)
+ if (atomic_inc_return(&chip->wq_processing) == 1)
snd_ak4113_check_rate_and_errors(chip, chip->check_flags);

- schedule_delayed_work(&chip->work, HZ / 10);
+ if (atomic_dec_and_test(&chip->wq_processing))
+ schedule_delayed_work(&chip->work, HZ / 10);
}
--- a/sound/i2c/other/ak4114.c
+++ b/sound/i2c/other/ak4114.c
@@ -66,8 +66,7 @@ static void reg_dump(struct ak4114 *ak41

static void snd_ak4114_free(struct ak4114 *chip)
{
- chip->init = 1; /* don't schedule new work */
- mb();
+ atomic_inc(&chip->wq_processing); /* don't schedule new work */
cancel_delayed_work_sync(&chip->work);
kfree(chip);
}
@@ -100,6 +99,7 @@ int snd_ak4114_create(struct snd_card *c
chip->write = write;
chip->private_data = private_data;
INIT_DELAYED_WORK(&chip->work, ak4114_stats);
+ atomic_set(&chip->wq_processing, 0);

for (reg = 0; reg < 6; reg++)
chip->regmap[reg] = pgm[reg];
@@ -152,13 +152,11 @@ static void ak4114_init_regs(struct ak41

void snd_ak4114_reinit(struct ak4114 *chip)
{
- chip->init = 1;
- mb();
- flush_delayed_work(&chip->work);
+ if (atomic_inc_return(&chip->wq_processing) == 1)
+ cancel_delayed_work_sync(&chip->work);
ak4114_init_regs(chip);
/* bring up statistics / event queing */
- chip->init = 0;
- if (chip->kctls[0])
+ if (atomic_dec_and_test(&chip->wq_processing))
schedule_delayed_work(&chip->work, HZ / 10);
}

@@ -612,10 +610,10 @@ static void ak4114_stats(struct work_str
{
struct ak4114 *chip = container_of(work, struct ak4114, work.work);

- if (!chip->init)
+ if (atomic_inc_return(&chip->wq_processing) == 1)
snd_ak4114_check_rate_and_errors(chip, chip->check_flags);
-
- schedule_delayed_work(&chip->work, HZ / 10);
+ if (atomic_dec_and_test(&chip->wq_processing))
+ schedule_delayed_work(&chip->work, HZ / 10);
}

EXPORT_SYMBOL(snd_ak4114_create);



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