| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.17 073/146] ALSA: emu10k1: Fix deadlock in synth voice lookup | Date | Tue, 28 Oct 2014 11:33:35 +0800 |
| |
3.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Takashi Iwai <tiwai@suse.de>
commit 95926035b187cc9fee6fb61385b7da9c28123f74 upstream.
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> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- sound/pci/emu10k1/emu10k1_callback.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- a/sound/pci/emu10k1/emu10k1_callback.c +++ b/sound/pci/emu10k1/emu10k1_callback.c @@ -85,6 +85,8 @@ snd_emu10k1_ops_setup(struct snd_emux *e * 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_e 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_e 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;
|