[3.5.y.z,extended,stable] Patch "ALSA: seq-oss: Initialize MIDI clients asynchronously" has been added to staging queue

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

    ALSA: seq-oss: Initialize MIDI clients asynchronously

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

From 84d0ac92d9bc06b1a5a6df8b12c44e2ab47249df Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 16 Jul 2013 12:17:49 +0200
Subject: [PATCH] ALSA: seq-oss: Initialize MIDI clients asynchronously

commit 256ca9c3ad5013ff8a8f165e5a82fab437628c8e upstream.

We've got bug reports that the module loading stuck on Debian system
with 3.10 kernel.  The debugging session revealed that the initial
registration of OSS sequencer clients stuck at module loading time,
which involves again with request_module() at the init phase.  This is
triggered only by special --install stuff Debian is using, but it's
still not good to have such loops.

As a workaround, call the registration part asynchronously.  This is a
better approach irrespective of the hang fix, in anyway.

Reported-and-tested-by: Philipp Matthias Hahn <pmhahn@pmhahn.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 sound/core/seq/oss/seq_oss_init.c | 16 +++++++++++++---
 sound/core/seq/oss/seq_oss_midi.c |  2 +-
 2 files changed, 14 insertions(+), 4 deletions(-)

--
1.8.1.2

At Wed, 24 Jul 2013 10:12:09 +0100,
Luis Henriques wrote:
> 
> This is a note to let you know that I have just added a patch titled
> 
>     ALSA: seq-oss: Initialize MIDI clients asynchronously
> 
> to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
> which can be found at:
> 
>  http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue
> 
> If you, or anyone else, feels it should not be added to this tree, please 
> reply to this email.
> 
> For more information about the 3.5.y.z tree, see
> https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

This problem was reported to appear since 3.10, so no need to patch
older kernels, although it's not that bad to apply it.


Takashi

> 
> Thanks.
> -Luis
> 
> ------
> 
> >From 84d0ac92d9bc06b1a5a6df8b12c44e2ab47249df Mon Sep 17 00:00:00 2001
> From: Takashi Iwai <tiwai@suse.de>
> Date: Tue, 16 Jul 2013 12:17:49 +0200
> Subject: [PATCH] ALSA: seq-oss: Initialize MIDI clients asynchronously
> 
> commit 256ca9c3ad5013ff8a8f165e5a82fab437628c8e upstream.
> 
> We've got bug reports that the module loading stuck on Debian system
> with 3.10 kernel.  The debugging session revealed that the initial
> registration of OSS sequencer clients stuck at module loading time,
> which involves again with request_module() at the init phase.  This is
> triggered only by special --install stuff Debian is using, but it's
> still not good to have such loops.
> 
> As a workaround, call the registration part asynchronously.  This is a
> better approach irrespective of the hang fix, in anyway.
> 
> Reported-and-tested-by: Philipp Matthias Hahn <pmhahn@pmhahn.de>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
> ---
>  sound/core/seq/oss/seq_oss_init.c | 16 +++++++++++++---
>  sound/core/seq/oss/seq_oss_midi.c |  2 +-
>  2 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/core/seq/oss/seq_oss_init.c b/sound/core/seq/oss/seq_oss_init.c
> index e3cb46f..b3f39b5 100644
> --- a/sound/core/seq/oss/seq_oss_init.c
> +++ b/sound/core/seq/oss/seq_oss_init.c
> @@ -31,6 +31,7 @@
>  #include <linux/export.h>
>  #include <linux/moduleparam.h>
>  #include <linux/slab.h>
> +#include <linux/workqueue.h>
> 
>  /*
>   * common variables
> @@ -60,6 +61,14 @@ static void free_devinfo(void *private);
>  #define call_ctl(type,rec) snd_seq_kernel_client_ctl(system_client, type, rec)
> 
> 
> +/* call snd_seq_oss_midi_lookup_ports() asynchronously */
> +static void async_call_lookup_ports(struct work_struct *work)
> +{
> +	snd_seq_oss_midi_lookup_ports(system_client);
> +}
> +
> +static DECLARE_WORK(async_lookup_work, async_call_lookup_ports);
> +
>  /*
>   * create sequencer client for OSS sequencer
>   */
> @@ -85,9 +94,6 @@ snd_seq_oss_create_client(void)
>  	system_client = rc;
>  	debug_printk(("new client = %d\n", rc));
> 
> -	/* look up midi devices */
> -	snd_seq_oss_midi_lookup_ports(system_client);
> -
>  	/* create annoucement receiver port */
>  	memset(port, 0, sizeof(*port));
>  	strcpy(port->name, "Receiver");
> @@ -115,6 +121,9 @@ snd_seq_oss_create_client(void)
>  	}
>  	rc = 0;
> 
> +	/* look up midi devices */
> +	schedule_work(&async_lookup_work);
> +
>   __error:
>  	kfree(port);
>  	return rc;
> @@ -160,6 +169,7 @@ receive_announce(struct snd_seq_event *ev, int direct, void *private, int atomic
>  int
>  snd_seq_oss_delete_client(void)
>  {
> +	cancel_work_sync(&async_lookup_work);
>  	if (system_client >= 0)
>  		snd_seq_delete_kernel_client(system_client);
> 
> diff --git a/sound/core/seq/oss/seq_oss_midi.c b/sound/core/seq/oss/seq_oss_midi.c
> index 677dc84..862d8489 100644
> --- a/sound/core/seq/oss/seq_oss_midi.c
> +++ b/sound/core/seq/oss/seq_oss_midi.c
> @@ -72,7 +72,7 @@ static int send_midi_event(struct seq_oss_devinfo *dp, struct snd_seq_event *ev,
>   * look up the existing ports
>   * this looks a very exhausting job.
>   */
> -int __init
> +int
>  snd_seq_oss_midi_lookup_ports(int client)
>  {
>  	struct snd_seq_client_info *clinfo;
> --
> 1.8.1.2
>

Takashi Iwai <tiwai@suse.de> writes:

> At Wed, 24 Jul 2013 10:12:09 +0100,
> Luis Henriques wrote:
>> 
>> This is a note to let you know that I have just added a patch titled
>> 
>>     ALSA: seq-oss: Initialize MIDI clients asynchronously
>> 
>> to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
>> which can be found at:
>> 
>>  http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue
>> 
>> If you, or anyone else, feels it should not be added to this tree, please 
>> reply to this email.
>> 
>> For more information about the 3.5.y.z tree, see
>> https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
>
> This problem was reported to appear since 3.10, so no need to patch
> older kernels, although it's not that bad to apply it.
>
>
> Takashi
>

Thank you for your feedback.  I'll drop this patch from the 3.5 queue.

Cheers,