ASoC: STI: Fix null ptr deference in IRQ handler

With RTlinux a race condition has been found that leads to NULL ptr crash:
- On CPU 0: uni_player_irq_handler is called to treat XRUN
 "(player->state == UNIPERIF_STATE_STOPPED)" is FALSE so status is checked,
 dev_err(player->dev, "FIFO underflow error detected") is printed
and then snd_pcm_stream_lock should be called to lock stream for stopping.
- On CPU 1: application stop and close the stream.
Issue is that the stop and shutdown functions are executed while
"FIFO underflow error detected" is printed.
So when CPU 0 calls snd_pcm_stream_lock, player->substream is already null.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/sound/soc/sti/uniperif.h b/sound/soc/sti/uniperif.h
index d487dd2ef016..cfcb0ea9d99d 100644
--- a/sound/soc/sti/uniperif.h
+++ b/sound/soc/sti/uniperif.h
@@ -1299,6 +1299,7 @@ struct uniperif {
 	int ver; /* IP version, used by register access macros */
 	struct regmap_field *clk_sel;
 	struct regmap_field *valid_sel;
+	spinlock_t irq_lock; /* use to prevent race condition with IRQ */
 
 	/* capabilities */
 	const struct snd_pcm_hardware *hw;