ALSA: ak411x: Fix stall in work callback

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 16 insertions, 19 deletions

diff --git a/sound/i2c/other/ak4113.c b/sound/i2c/other/ak4113.c
index 1a3a6fa27158..c6bba99a90b2 100644
--- a/sound/i2c/other/ak4113.c
+++ b/sound/i2c/other/ak4113.c
@@ -56,8 +56,7 @@ static inline unsigned char reg_read(struct ak4113 *ak4113, unsigned char reg)
 
 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 *card, ak4113_read_t *read,
         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 ak4113 *chip)
 
 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_struct *work)
 {
         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);
 }
diff --git a/sound/i2c/other/ak4114.c b/sound/i2c/other/ak4114.c
index c7f56339415d..b70e6eccbd03 100644
--- a/sound/i2c/other/ak4114.c
+++ b/sound/i2c/other/ak4114.c
@@ -66,8 +66,7 @@ static void reg_dump(struct ak4114 *ak4114)
 
 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 *card,
         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 ak4114 *chip)
 
 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_struct *work)
 {
         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);