ALSA: emu10k1: Fix deadlock in synth voice lookup
The emu10k1 voice allocator takes voice_lock spinlock. When there is
no empty stream available, it tries to release a voice used by synth,
and calls get_synth_voice. The callback function,
snd_emu10k1_synth_get_voice(), however, also takes the voice_lock,
thus it deadlocks.
The fix is simply removing the voice_lock holds in
snd_emu10k1_synth_get_voice(), as this is always called in the
spinlock context.
Reported-and-tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/emu10k1/emu10k1_callback.c b/sound/pci/emu10k1/emu10k1_callback.c
index 3f3ef38..874cd76 100644
--- a/sound/pci/emu10k1/emu10k1_callback.c
+++ b/sound/pci/emu10k1/emu10k1_callback.c
@@ -85,6 +85,8 @@
* get more voice for pcm
*
* terminate most inactive voice and give it as a pcm voice.
+ *
+ * voice_lock is already held.
*/
int
snd_emu10k1_synth_get_voice(struct snd_emu10k1 *hw)
@@ -92,12 +94,10 @@
struct snd_emux *emu;
struct snd_emux_voice *vp;
struct best_voice best[V_END];
- unsigned long flags;
int i;
emu = hw->synth;
- spin_lock_irqsave(&emu->voice_lock, flags);
lookup_voices(emu, hw, best, 1); /* no OFF voices */
for (i = 0; i < V_END; i++) {
if (best[i].voice >= 0) {
@@ -113,11 +113,9 @@
vp->emu->num_voices--;
vp->ch = -1;
vp->state = SNDRV_EMUX_ST_OFF;
- spin_unlock_irqrestore(&emu->voice_lock, flags);
return ch;
}
}
- spin_unlock_irqrestore(&emu->voice_lock, flags);
/* not found */
return -ENOMEM;