ALSA: emux: Fix mutex deadlock at unloading
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(®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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -124,12 +124,10 @@ snd_emux_detach_seq(struct snd_emux *emu)
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if (emu->voices)
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if (emu->voices)
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snd_emux_terminate_all(emu);
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snd_emux_terminate_all(emu);
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mutex_lock(&emu->register_mutex);
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if (emu->client >= 0) {
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if (emu->client >= 0) {
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snd_seq_delete_kernel_client(emu->client);
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snd_seq_delete_kernel_client(emu->client);
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emu->client = -1;
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emu->client = -1;
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}
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}
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mutex_unlock(&emu->register_mutex);
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}
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}
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