ALSA: emux: Fix mutex deadlock at unloading

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commit 07b0e5d49d 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(&register_mutex)

  snd_seq_release() ->
    snd_seq_free_client(): mutex_lock(&register_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: Luis Henriques <luis.henriques@canonical.com>

...

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Takashi Iwai 2015-04-27 14:50:39 +02:00 • committed by Luis Henriques

parent e45af6c86a

commit 6f9e33f2cb

1 changed files with 0 additions and 2 deletions

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sound/synth/emux/emux_seq.c

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