ALSA: pcsp - Fix locking messes in snd-pcsp

snd-pcsp driver takes chip->substream_lock together with PCM substream
lock.  These are even mixed up with hrtimer's lock, resulting in messy
lock depencies.  Right now, snd-pcsp driver resolves the deadlock by
using HRTIMER_CB_SOFTIRQ.  However, this isn't nice for a really fast
path like bit-flipping.

This patch introduces a tasklet for PCM period handling so that the
hrtimer callback can be handled fast.  This also reduce the use of
chip->substream_lock to avoid deadlocks.  It's still used in pointer
callback, but even this could be removed with a proper barrier.

Another good solution is to introduce async trigger callback.  But,
this will involve with a major rewrite of the PCM core code, so I
take first this easy fix.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 3 insertions, 5 deletions

diff --git a/sound/drivers/pcsp/pcsp.c b/sound/drivers/pcsp/pcsp.c
index 1899cf0685bc..87219bf0a35e 100644
--- a/sound/drivers/pcsp/pcsp.c
+++ b/sound/drivers/pcsp/pcsp.c
@@ -96,7 +96,7 @@ static int __devinit snd_card_pcsp_probe(int devnum, struct device *dev)
                 return -EINVAL;
 
         hrtimer_init(&pcsp_chip.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-        pcsp_chip.timer.cb_mode = HRTIMER_CB_SOFTIRQ;
+        pcsp_chip.timer.cb_mode = HRTIMER_CB_IRQSAFE;
         pcsp_chip.timer.function = pcsp_do_timer;
 
         card = snd_card_new(index, id, THIS_MODULE, 0);
@@ -188,10 +188,8 @@ static int __devexit pcsp_remove(struct platform_device *dev)
 
 static void pcsp_stop_beep(struct snd_pcsp *chip)
 {
-        spin_lock_irq(&chip->substream_lock);
-        if (!chip->playback_substream)
-                pcspkr_stop_sound();
-        spin_unlock_irq(&chip->substream_lock);
+        pcsp_sync_stop(chip);
+        pcspkr_stop_sound();
 }
 
 #ifdef CONFIG_PM