On 18/09/2019 11:41:14+0200, Gregory CLEMENT wrote:
> 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
>
> Signed-off-by: Gregory CLEMENT <gregory.clem...@bootlin.com>
> ---
> sound/soc/atmel/atmel_ssc_dai.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
> index 6f89483ac88c..365957e86419 100644
> --- 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),
This member is now unused and can be removed from the struct.
Once fixed, Reviewed-by: Alexandre Belloni <alexandre.bell...@bootlin.com>
> .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 +314,11 @@ 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);
> return -EBUSY;
> }
> ssc_p->dir_mask |= dir_mask;
> - spin_unlock_irq(&ssc_p->lock);
>
> return 0;
> }
> @@ -355,7 +350,6 @@ 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 +363,6 @@ 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");
> --
> 2.23.0
>
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
