ASoC: atmel_ssc_dai: Remove wrong spinlock usage

A potential bug was reported in the email "[BUG] atmel_ssc_dai: a
possible sleep-in-atomic bug in atmel_ssc_shutdown"[1]

Indeed in the function atmel_ssc_shutdown() free_irq() was called in a
critical section protected by spinlock.

However this spinlock is only used in atmel_ssc_shutdown() and
atmel_ssc_startup() functions. After further analysis, it occurred that
the call to these function are already protected by mutex used on the
calling functions.

Then we can remove the spinlock which will fix this bug as a side
effect. Thanks to this patch the following message disappears:

"BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:909"

[1]: https://www.spinics.net/lists/alsa-devel/msg71286.html

Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Link: https://lore.kernel.org/r/20190918100344.23629-1-gregory.clement@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
index 48e9eef34c0fead794794ed987597d2bb37ba83a..ca603397651c0f19376fc4543269b6d38e233e76 100644 (file)
--- a/sound/soc/atmel/atmel_ssc_dai.c
+++ b/sound/soc/atmel/atmel_ssc_dai.c
@@ -116,19 +116,16 @@ static struct atmel_pcm_dma_params ssc_dma_params[NUM_SSC_DEVICES][2] = {
 static struct atmel_ssc_info ssc_info[NUM_SSC_DEVICES] = {
        {
        .name           = "ssc0",
-       .lock           = __SPIN_LOCK_UNLOCKED(ssc_info[0].lock),
        .dir_mask       = SSC_DIR_MASK_UNUSED,
        .initialized    = 0,
        },
        {
        .name           = "ssc1",
-       .lock           = __SPIN_LOCK_UNLOCKED(ssc_info[1].lock),
        .dir_mask       = SSC_DIR_MASK_UNUSED,
        .initialized    = 0,
        },
        {
        .name           = "ssc2",
-       .lock           = __SPIN_LOCK_UNLOCKED(ssc_info[2].lock),
        .dir_mask       = SSC_DIR_MASK_UNUSED,
        .initialized    = 0,
        },
@@ -317,13 +314,10 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
 
        snd_soc_dai_set_dma_data(dai, substream, dma_params);
 
-       spin_lock_irq(&ssc_p->lock);
-       if (ssc_p->dir_mask & dir_mask) {
-               spin_unlock_irq(&ssc_p->lock);
+       if (ssc_p->dir_mask & dir_mask)
                return -EBUSY;
-       }
+
        ssc_p->dir_mask |= dir_mask;
-       spin_unlock_irq(&ssc_p->lock);
 
        return 0;
 }
@@ -355,7 +349,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
 
        dir_mask = 1 << dir;
 
-       spin_lock_irq(&ssc_p->lock);
        ssc_p->dir_mask &= ~dir_mask;
        if (!ssc_p->dir_mask) {
                if (ssc_p->initialized) {
@@ -369,7 +362,6 @@ static void atmel_ssc_shutdown(struct snd_pcm_substream *substream,
                ssc_p->cmr_div = ssc_p->tcmr_period = ssc_p->rcmr_period = 0;
                ssc_p->forced_divider = 0;
        }
-       spin_unlock_irq(&ssc_p->lock);
 
        /* Shutdown the SSC clock. */
        pr_debug("atmel_ssc_dai: Stopping clock\n");

diff --git a/sound/soc/atmel/atmel_ssc_dai.h b/sound/soc/atmel/atmel_ssc_dai.h
index ae764cb541c78cba6c1e87cec190a54f5c5c96cd..3470b966e44971a1126e4356ea544356f7a674c4 100644 (file)
--- a/sound/soc/atmel/atmel_ssc_dai.h
+++ b/sound/soc/atmel/atmel_ssc_dai.h
@@ -93,7 +93,6 @@ struct atmel_ssc_state {
 struct atmel_ssc_info {
        char *name;
        struct ssc_device *ssc;
-       spinlock_t lock;        /* lock for dir_mask */
        unsigned short dir_mask;        /* 0=unused, 1=playback, 2=capture */
        unsigned short initialized;     /* true if SSC has been initialized */
        unsigned short daifmt;