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

[Takashi Iwai]

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 at 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 at pmhahn.de>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> Signed-off-by: Luis Henriques <luis.henriques at 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
>