[ALSA] Fix possible deadlocks in sequencer at removal of ports

Fix possible rwsem deadlocks in sequencer code at removal of
sequencer ports.  The list_lock of port group can be double
locked.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

diff --git a/sound/core/seq/seq_ports.c b/sound/core/seq/seq_ports.c
index d881534..eefd1cf 100644 (file)
--- a/sound/core/seq/seq_ports.c
+++ b/sound/core/seq/seq_ports.c
@@ -245,9 +245,9 @@ static void clear_subscriber_list(struct snd_seq_client *client,
                                list_del(&subs->dest_list);
                        else
                                list_del(&subs->src_list);
+                       up_write(&agrp->list_mutex);
                        unsubscribe_port(c, aport, agrp, &subs->info, 1);
                        kfree(subs);
-                       up_write(&agrp->list_mutex);
                        snd_seq_port_unlock(aport);
                        snd_seq_client_unlock(c);
                }