ALSA: usb-audio: Fix deadlocks at resuming
The recent addition of the USB audio mixer suspend/resume may lead to
deadlocks when the driver tries to call usb_autopm_get_interface()
recursively, since the function tries to sync with the finish of the
other calls. For avoiding it, introduce a flag indicating the resume
operation and avoids the recursive usb_autopm_get_interface() calls
during the resume.
Reported-and-tested-by: Bryan Quigley <gquigs@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/card.c b/sound/usb/card.c
index e769d39..c3b5b7d 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -651,7 +651,7 @@
int err = -ENODEV;
down_read(&chip->shutdown_rwsem);
- if (chip->probing)
+ if (chip->probing && chip->in_pm)
err = 0;
else if (!chip->shutdown)
err = usb_autopm_get_interface(chip->pm_intf);
@@ -663,7 +663,7 @@
void snd_usb_autosuspend(struct snd_usb_audio *chip)
{
down_read(&chip->shutdown_rwsem);
- if (!chip->shutdown && !chip->probing)
+ if (!chip->shutdown && !chip->probing && !chip->in_pm)
usb_autopm_put_interface(chip->pm_intf);
up_read(&chip->shutdown_rwsem);
}
@@ -712,6 +712,8 @@
return 0;
if (--chip->num_suspended_intf)
return 0;
+
+ chip->in_pm = 1;
/*
* ALSA leaves material resumption to user space
* we just notify and restart the mixers
@@ -727,6 +729,7 @@
chip->autosuspended = 0;
err_out:
+ chip->in_pm = 0;
return err;
}
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 25c4c7e..91d0380 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -40,6 +40,7 @@
struct rw_semaphore shutdown_rwsem;
unsigned int shutdown:1;
unsigned int probing:1;
+ unsigned int in_pm:1;
unsigned int autosuspended:1;
unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */
