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Commit 95926035 authored by Takashi Iwai's avatar Takashi Iwai
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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: default avatarArthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 811deede

sound/pci/emu10k1/emu10k1_callback.c

+2 −4
Original line number Diff line number Diff line
@@ -85,6 +85,8 @@ snd_emu10k1_ops_setup(struct snd_emux *emux) 
 * 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 @@ snd_emu10k1_synth_get_voice(struct snd_emu10k1 *hw) 
	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 @@ snd_emu10k1_synth_get_voice(struct snd_emu10k1 *hw) 
			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;