[alsa-devel] [RFC PATCH] ALSA: usb - fix race in creation of M-Audio Fast track pro driver
A patch in the 3.2 kernel caused regression with hotplugging the M-Audio Fast track pro, or sound after suspend. I don't have the device so I haven't done a full analysis, but it seems userspace (both udev and pulseaudio) got confused when a card was created, immediately destroyed, and then created again.
However, at least one person in the bug report (martin djfun) reports that this patch resolves the issue for him. It also leaves a message in the log: "snd-usb-audio: probe of 1-1.1:1.1 failed with error -5" which is a bit misleading. It is better than non-working audio, but maybe there's a more elegant solution?
BugLink: https://bugs.launchpad.net/bugs/1095315 Signed-off-by: David Henningsson david.henningsson@canonical.com --- sound/usb/quirks.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
...oh, and if you end up taking this patch as it is, you should probably add cc to stable (3.2+).
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c index acc12f0..e71fc8b 100644 --- a/sound/usb/quirks.c +++ b/sound/usb/quirks.c @@ -387,11 +387,13 @@ static int snd_usb_fasttrackpro_boot_quirk(struct usb_device *dev) * rules */ err = usb_driver_set_configuration(dev, 2); - if (err < 0) { + if (err < 0) snd_printdd("error usb_driver_set_configuration: %d\n", err); - return -ENODEV; - } + /* Always return an error, so that we stop creating a device + that will just be destroyed and recreated with a new + configuration */ + return -ENODEV; } else snd_printk(KERN_INFO "usb-audio: Fast Track Pro config OK\n");
David Henningsson wrote:
this patch resolves the issue for him. It also leaves a message in the log: "snd-usb-audio: probe of 1-1.1:1.1 failed with error -5"
I'd guess this is for an interface not claimed by the driver but without an explicit QUIRK_IGNORE_INTERFACE entry.
Regards, Clemens
On 01/04/2013 09:19 PM, Clemens Ladisch wrote:
David Henningsson wrote:
this patch resolves the issue for him. It also leaves a message in the log: "snd-usb-audio: probe of 1-1.1:1.1 failed with error -5"
I'd guess this is for an interface not claimed by the driver but without an explicit QUIRK_IGNORE_INTERFACE entry.
My patch causes this error because the quirk fails with an error, which is later on turned into a -EIO. Any quirk_ignore_interface entry will therefore be ignored. Using the quirk_ignore_interface entry *instead of* my patch seems like an interesting option, but...
Looking at the code again, it seems like we have a more generic race problem, unless I'm missing something:
- the same ALSA sound card can contain more than one USB interface. - snd_card_register is called whenever a USB interface finishes probing. - snd_card_register fires off uevents, causing stuff to happen such as volume restore (alsactl) and PulseAudio starts probing the device - so when userspace starts accessing the device, the device is not fully functional, because not all USB interfaces have yet been probed - as a result, volumes might not get restored (if all mixer controls do not belong to the first interface), and PulseAudio thinks the device is not capable of all the stuff it actually can do (if all pcm streams do not belong to the first interface).
I guess this is probably not a problem normally because the kernel is faster than userspace, but it is revealed here because switching configurations takes longer time than probing another interface.
On 01/04/2013 05:02 PM, David Henningsson wrote:
A patch in the 3.2 kernel caused regression with hotplugging the M-Audio Fast track pro, or sound after suspend. I don't have the device so I haven't done a full analysis, but it seems userspace (both udev and pulseaudio) got confused when a card was created, immediately destroyed, and then created again.
Since there were no counter proposal patches and the below code actually fixes a problem for users, would you mind committing it?
However, at least one person in the bug report (martin djfun) reports that this patch resolves the issue for him. It also leaves a message in the log: "snd-usb-audio: probe of 1-1.1:1.1 failed with error -5" which is a bit misleading. It is better than non-working audio, but maybe there's a more elegant solution?
BugLink: https://bugs.launchpad.net/bugs/1095315 Signed-off-by: David Henningsson david.henningsson@canonical.com
sound/usb/quirks.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
...oh, and if you end up taking this patch as it is, you should probably add cc to stable (3.2+).
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c index acc12f0..e71fc8b 100644 --- a/sound/usb/quirks.c +++ b/sound/usb/quirks.c @@ -387,11 +387,13 @@ static int snd_usb_fasttrackpro_boot_quirk(struct usb_device *dev) * rules */ err = usb_driver_set_configuration(dev, 2);
if (err < 0) {
if (err < 0) snd_printdd("error usb_driver_set_configuration: %d\n", err);
return -ENODEV;}
/* Always return an error, so that we stop creating a devicethat will just be destroyed and recreated with a newconfiguration */return -ENODEV;
At Mon, 14 Jan 2013 08:21:56 +0100, David Henningsson wrote:
On 01/04/2013 05:02 PM, David Henningsson wrote:
A patch in the 3.2 kernel caused regression with hotplugging the M-Audio Fast track pro, or sound after suspend. I don't have the device so I haven't done a full analysis, but it seems userspace (both udev and pulseaudio) got confused when a card was created, immediately destroyed, and then created again.
Since there were no counter proposal patches and the below code actually fixes a problem for users, would you mind committing it?
OK, applied now.
Takashi
However, at least one person in the bug report (martin djfun) reports that this patch resolves the issue for him. It also leaves a message in the log: "snd-usb-audio: probe of 1-1.1:1.1 failed with error -5" which is a bit misleading. It is better than non-working audio, but maybe there's a more elegant solution?
BugLink: https://bugs.launchpad.net/bugs/1095315 Signed-off-by: David Henningsson david.henningsson@canonical.com
sound/usb/quirks.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
...oh, and if you end up taking this patch as it is, you should probably add cc to stable (3.2+).
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c index acc12f0..e71fc8b 100644 --- a/sound/usb/quirks.c +++ b/sound/usb/quirks.c @@ -387,11 +387,13 @@ static int snd_usb_fasttrackpro_boot_quirk(struct usb_device *dev) * rules */ err = usb_driver_set_configuration(dev, 2);
if (err < 0) {
if (err < 0) snd_printdd("error usb_driver_set_configuration: %d\n", err);
return -ENODEV;}
/* Always return an error, so that we stop creating a devicethat will just be destroyed and recreated with a newconfiguration */return -ENODEV;-- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic
participants (3)
-
Clemens Ladisch -
David Henningsson -
Takashi Iwai