ALSA: seq: Continue broadcasting events to ports if one of them fails

Sometimes PORT_EXIT messages are lost when a process is exiting.
This happens if you subscribe to the announce port with client A,
then subscribe to the announce port with client B, then kill client A.
Client B will not see the PORT_EXIT message because client A's port is
closing and is earlier in the announce port subscription list. The
for each loop will try to send the announcement to client A and fail,
then will stop trying to broadcast to other ports. Killing B works fine
since the announcement will already have gone to A. The CLIENT_EXIT
message does not get lost.

How to reproduce problem:

*** termA
$ aseqdump -p 0:1
  0:1   Port subscribed            0:1 -> 128:0

*** termB
$ aseqdump -p 0:1

*** termA
  0:1   Client start               client 129
  0:1   Port start                 129:0
  0:1   Port subscribed            0:1 -> 129:0

*** termB
  0:1   Port subscribed            0:1 -> 129:0

*** termA
^C

*** termB
  0:1   Client exit                client 128
   <--- expected Port exit as well (before client exit)

Signed-off-by: Adam Goode <agoode@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 24 insertions, 12 deletions

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 9ca5e647e54b..225c73152ee9 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -660,7 +660,7 @@ static int deliver_to_subscribers(struct snd_seq_client *client,
                                   int atomic, int hop)
 {
         struct snd_seq_subscribers *subs;
-        int err = 0, num_ev = 0;
+        int err, result = 0, num_ev = 0;
         struct snd_seq_event event_saved;
         struct snd_seq_client_port *src_port;
         struct snd_seq_port_subs_info *grp;
@@ -685,8 +685,12 @@ static int deliver_to_subscribers(struct snd_seq_client *client,
                                                   subs->info.flags & SNDRV_SEQ_PORT_SUBS_TIME_REAL);
                 err = snd_seq_deliver_single_event(client, event,
                                                    0, atomic, hop);
-                if (err < 0)
-                        break;
+                if (err < 0) {
+                        /* save first error that occurs and continue */
+                        if (!result)
+                                result = err;
+                        continue;
+                }
                 num_ev++;
                 /* restore original event record */
                 *event = event_saved;
@@ -697,7 +701,7 @@ static int deliver_to_subscribers(struct snd_seq_client *client,
                 up_read(&grp->list_mutex);
         *event = event_saved; /* restore */
         snd_seq_port_unlock(src_port);
-        return (err < 0) ? err : num_ev;
+        return (result < 0) ? result : num_ev;
 }
 
 
@@ -709,7 +713,7 @@ static int port_broadcast_event(struct snd_seq_client *client,
                                 struct snd_seq_event *event,
                                 int atomic, int hop)
 {
-        int num_ev = 0, err = 0;
+        int num_ev = 0, err, result = 0;
         struct snd_seq_client *dest_client;
         struct snd_seq_client_port *port;
 
@@ -724,14 +728,18 @@ static int port_broadcast_event(struct snd_seq_client *client,
                 err = snd_seq_deliver_single_event(NULL, event,
                                                    SNDRV_SEQ_FILTER_BROADCAST,
                                                    atomic, hop);
-                if (err < 0)
-                        break;
+                if (err < 0) {
+                        /* save first error that occurs and continue */
+                        if (!result)
+                                result = err;
+                        continue;
+                }
                 num_ev++;
         }
         read_unlock(&dest_client->ports_lock);
         snd_seq_client_unlock(dest_client);
         event->dest.port = SNDRV_SEQ_ADDRESS_BROADCAST; /* restore */
-        return (err < 0) ? err : num_ev;
+        return (result < 0) ? result : num_ev;
 }
 
 /*
@@ -741,7 +749,7 @@ static int port_broadcast_event(struct snd_seq_client *client,
 static int broadcast_event(struct snd_seq_client *client,
                            struct snd_seq_event *event, int atomic, int hop)
 {
-        int err = 0, num_ev = 0;
+        int err, result = 0, num_ev = 0;
         int dest;
         struct snd_seq_addr addr;
 
@@ -760,12 +768,16 @@ static int broadcast_event(struct snd_seq_client *client,
                         err = snd_seq_deliver_single_event(NULL, event,
                                                            SNDRV_SEQ_FILTER_BROADCAST,
                                                            atomic, hop);
-                if (err < 0)
-                        break;
+                if (err < 0) {
+                        /* save first error that occurs and continue */
+                        if (!result)
+                                result = err;
+                        continue;
+                }
                 num_ev += err;
         }
         event->dest = addr; /* restore */
-        return (err < 0) ? err : num_ev;
+        return (result < 0) ? result : num_ev;
 }