| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 12/92] ALSA: emux: Fix mutex deadlock at unloading | Date | Tue, 26 May 2015 08:40:16 -0700 |
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3.19.8-ckt1 -stable review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai <tiwai@suse.de>
commit 07b0e5d49d227e3950cb13a3e8caf248ef2a310e upstream.
The emux-synth driver has a possible AB/BA mutex deadlock at unloading the emu10k1 driver:
snd_emux_free() -> snd_emux_detach_seq(): mutex_lock(&emu->register_mutex) -> snd_seq_delete_kernel_client() -> snd_seq_free_client(): mutex_lock(®ister_mutex)
snd_seq_release() -> snd_seq_free_client(): mutex_lock(®ister_mutex) -> snd_seq_delete_all_ports() -> snd_emux_unuse(): mutex_lock(&emu->register_mutex)
Basically snd_emux_detach_seq() doesn't need a protection of emu->register_mutex as it's already being unregistered. So, we can get rid of this for avoiding the deadlock.
Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- sound/synth/emux/emux_seq.c | 2 -- 1 file changed, 2 deletions(-)
diff --git a/sound/synth/emux/emux_seq.c b/sound/synth/emux/emux_seq.c index 7778b8e..188fda0e 100644 --- a/sound/synth/emux/emux_seq.c +++ b/sound/synth/emux/emux_seq.c @@ -124,12 +124,10 @@ snd_emux_detach_seq(struct snd_emux *emu) if (emu->voices) snd_emux_terminate_all(emu); - mutex_lock(&emu->register_mutex); if (emu->client >= 0) { snd_seq_delete_kernel_client(emu->client); emu->client = -1; } - mutex_unlock(&emu->register_mutex); } -- 1.9.1
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