[3.16.y-ckt stable] Patch "ALSA: seq-dummy: remove deadlock-causing events on close" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ALSA: seq-dummy: remove deadlock-causing events on close

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3411d56b2bc632f14f5552d3b792aff05fdf261c Mon Sep 17 00:00:00 2001
From: Clemens Ladisch <clemens at ladisch.de>
Date: Sun, 25 Jan 2015 14:34:29 +0100
Subject: ALSA: seq-dummy: remove deadlock-causing events on close

commit 0767e95bb96d7fdddcd590fb809e6975d93aebc5 upstream.

When the last subscriber to a "Through" port has been removed, the
subscribed destination ports might still be active, so it would be
wrong to send "all sounds off" and "reset controller" events to them.
The proper place for such a shutdown would be the closing of the actual
MIDI port (and close_substream() in rawmidi.c already can do this).

This also fixes a deadlock when dummy_unuse() tries to send events to
its own port that is already locked because it is being freed.

Reported-by: Peter Billam <peter at www.pjb.com.au>
Signed-off-by: Clemens Ladisch <clemens at ladisch.de>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 sound/core/seq/seq_dummy.c | 31 -------------------------------
 1 file changed, 31 deletions(-)

diff --git a/sound/core/seq/seq_dummy.c b/sound/core/seq/seq_dummy.c
index ec667f158f19..5d905d90d504 100644
--- a/sound/core/seq/seq_dummy.c
+++ b/sound/core/seq/seq_dummy.c
@@ -82,36 +82,6 @@ struct snd_seq_dummy_port {
 static int my_client = -1;

 /*
- * unuse callback - send ALL_SOUNDS_OFF and RESET_CONTROLLERS events
- * to subscribers.
- * Note: this callback is called only after all subscribers are removed.
- */
-static int
-dummy_unuse(void *private_data, struct snd_seq_port_subscribe *info)
-{
-	struct snd_seq_dummy_port *p;
-	int i;
-	struct snd_seq_event ev;
-
-	p = private_data;
-	memset(&ev, 0, sizeof(ev));
-	if (p->duplex)
-		ev.source.port = p->connect;
-	else
-		ev.source.port = p->port;
-	ev.dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
-	ev.type = SNDRV_SEQ_EVENT_CONTROLLER;
-	for (i = 0; i < 16; i++) {
-		ev.data.control.channel = i;
-		ev.data.control.param = MIDI_CTL_ALL_SOUNDS_OFF;
-		snd_seq_kernel_client_dispatch(p->client, &ev, 0, 0);
-		ev.data.control.param = MIDI_CTL_RESET_CONTROLLERS;
-		snd_seq_kernel_client_dispatch(p->client, &ev, 0, 0);
-	}
-	return 0;
-}
-
-/*
  * event input callback - just redirect events to subscribers
  */
 static int
@@ -175,7 +145,6 @@ create_port(int idx, int type)
 		| SNDRV_SEQ_PORT_TYPE_PORT;
 	memset(&pcb, 0, sizeof(pcb));
 	pcb.owner = THIS_MODULE;
-	pcb.unuse = dummy_unuse;
 	pcb.event_input = dummy_input;
 	pcb.private_free = dummy_free;
 	pcb.private_data = rec;
--
2.1.4