ALSA: usb-audio: Avoid nested autoresume calls

After the recent fix of runtime PM for USB-audio driver, we got a
lockdep warning like:

  =============================================
  [ INFO: possible recursive locking detected ]
  4.2.0-rc8+ #61 Not tainted
  ---------------------------------------------
  pulseaudio/980 is trying to acquire lock:
   (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
  but task is already holding lock:
   (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]

This comes from snd_usb_autoresume() invoking down_read() and it's
used in a nested way.  Although it's basically safe, per se (as these
are read locks), it's better to reduce such spurious warnings.

The read lock is needed to guarantee the execution of "shutdown"
(cleanup at disconnection) task after all concurrent tasks are
finished.  This can be implemented in another better way.

Also, the current check of chip->in_pm isn't good enough for
protecting the racy execution of multiple auto-resumes.

This patch rewrites the logic of snd_usb_autoresume() & co; namely,
- The recursive call of autopm is avoided by the new refcount,
  chip->active.  The chip->in_pm flag is removed accordingly.
- Instead of rwsem, another refcount, chip->usage_count, is introduced
  for tracking the period to delay the shutdown procedure.  At
  the last clear of this refcount, wake_up() to the shutdown waiter is
  called.
- The shutdown flag is replaced with shutdown atomic count; this is
  for reducing the lock.
- Two new helpers are introduced to simplify the management of these
  refcounts; snd_usb_lock_shutdown() increases the usage_count, checks
  the shutdown state, and does autoresume.  snd_usb_unlock_shutdown()
  does the opposite.  Most of mixer and other codes just need this,
  and simply returns an error if it receives an error from lock.

Fixes: 9003ebb13f61 ('ALSA: usb-audio: Fix runtime PM unbalance')
Reported-and-tested-by: Alexnader Kuleshov <kuleshovmail@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 54 insertions, 72 deletions

diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index 337c317ead6f..d3608c0a29f3 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -308,11 +308,10 @@ static int snd_audigy2nx_led_update(struct usb_mixer_interface *mixer,
 	struct snd_usb_audio *chip = mixer->chip;
 	int err;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown) {
-		err = -ENODEV;
-		goto out;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+
 	if (chip->usb_id == USB_ID(0x041e, 0x3042))
 		err = snd_usb_ctl_msg(chip->dev,
 			      usb_sndctrlpipe(chip->dev, 0), 0x24,
@@ -329,8 +328,7 @@ static int snd_audigy2nx_led_update(struct usb_mixer_interface *mixer,
 			      usb_sndctrlpipe(chip->dev, 0), 0x24,
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_OTHER,
 			      value, index + 2, NULL, 0);
- out:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -441,16 +439,15 @@ static void snd_audigy2nx_proc_read(struct snd_info_entry *entry,
 
 	for (i = 0; jacks[i].name; ++i) {
 		snd_iprintf(buffer, "%s: ", jacks[i].name);
-		down_read(&mixer->chip->shutdown_rwsem);
-		if (mixer->chip->shutdown)
-			err = 0;
-		else
-			err = snd_usb_ctl_msg(mixer->chip->dev,
+		err = snd_usb_lock_shutdown(mixer->chip);
+		if (err < 0)
+			return;
+		err = snd_usb_ctl_msg(mixer->chip->dev,
 				      usb_rcvctrlpipe(mixer->chip->dev, 0),
 				      UAC_GET_MEM, USB_DIR_IN | USB_TYPE_CLASS |
 				      USB_RECIP_INTERFACE, 0,
 				      jacks[i].unitid << 8, buf, 3);
-		up_read(&mixer->chip->shutdown_rwsem);
+		snd_usb_unlock_shutdown(mixer->chip);
 		if (err == 3 && (buf[0] == 3 || buf[0] == 6))
 			snd_iprintf(buffer, "%02x %02x\n", buf[1], buf[2]);
 		else
@@ -481,11 +478,9 @@ static int snd_emu0204_ch_switch_update(struct usb_mixer_interface *mixer,
 	int err;
 	unsigned char buf[2];
 
-	down_read(&chip->shutdown_rwsem);
-	if (mixer->chip->shutdown) {
-		err = -ENODEV;
-		goto out;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
 
 	buf[0] = 0x01;
 	buf[1] = value ? 0x02 : 0x01;
@@ -493,8 +488,7 @@ static int snd_emu0204_ch_switch_update(struct usb_mixer_interface *mixer,
 		      usb_sndctrlpipe(chip->dev, 0), UAC_SET_CUR,
 		      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
 		      0x0400, 0x0e00, buf, 2);
- out:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -554,15 +548,14 @@ static int snd_xonar_u1_switch_update(struct usb_mixer_interface *mixer,
 	struct snd_usb_audio *chip = mixer->chip;
 	int err;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown)
-		err = -ENODEV;
-	else
-		err = snd_usb_ctl_msg(chip->dev,
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+	err = snd_usb_ctl_msg(chip->dev,
 			      usb_sndctrlpipe(chip->dev, 0), 0x08,
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_OTHER,
 			      50, 0, &status, 1);
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -623,11 +616,9 @@ static int snd_mbox1_switch_update(struct usb_mixer_interface *mixer, int val)
 	int err;
 	unsigned char buff[3];
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown) {
-		err = -ENODEV;
-		goto err;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
 
 	/* Prepare for magic command to toggle clock source */
 	err = snd_usb_ctl_msg(chip->dev,
@@ -683,7 +674,7 @@ static int snd_mbox1_switch_update(struct usb_mixer_interface *mixer, int val)
 		goto err;
 
 err:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -778,15 +769,14 @@ static int snd_ni_update_cur_val(struct usb_mixer_elem_list *list)
 	unsigned int pval = list->kctl->private_value;
 	int err;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown)
-		err = -ENODEV;
-	else
-		err = usb_control_msg(chip->dev, usb_sndctrlpipe(chip->dev, 0),
-				      (pval >> 16) & 0xff,
-				      USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
-				      pval >> 24, pval & 0xffff, NULL, 0, 1000);
-	up_read(&chip->shutdown_rwsem);
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+	err = usb_control_msg(chip->dev, usb_sndctrlpipe(chip->dev, 0),
+			      (pval >> 16) & 0xff,
+			      USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
+			      pval >> 24, pval & 0xffff, NULL, 0, 1000);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -944,18 +934,17 @@ static int snd_ftu_eff_switch_update(struct usb_mixer_elem_list *list)
 	value[0] = pval >> 24;
 	value[1] = 0;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown)
-		err = -ENODEV;
-	else
-		err = snd_usb_ctl_msg(chip->dev,
-				      usb_sndctrlpipe(chip->dev, 0),
-				      UAC_SET_CUR,
-				      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
-				      pval & 0xff00,
-				      snd_usb_ctrl_intf(chip) | ((pval & 0xff) << 8),
-				      value, 2);
-	up_read(&chip->shutdown_rwsem);
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
+	err = snd_usb_ctl_msg(chip->dev,
+			      usb_sndctrlpipe(chip->dev, 0),
+			      UAC_SET_CUR,
+			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
+			      pval & 0xff00,
+			      snd_usb_ctrl_intf(chip) | ((pval & 0xff) << 8),
+			      value, 2);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -1519,11 +1508,9 @@ static int snd_microii_spdif_default_get(struct snd_kcontrol *kcontrol,
 	unsigned char data[3];
 	int rate;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown) {
-		err = -ENODEV;
-		goto end;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
 
 	ucontrol->value.iec958.status[0] = kcontrol->private_value & 0xff;
 	ucontrol->value.iec958.status[1] = (kcontrol->private_value >> 8) & 0xff;
@@ -1551,7 +1538,7 @@ static int snd_microii_spdif_default_get(struct snd_kcontrol *kcontrol,
 
 	err = 0;
  end:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -1562,11 +1549,9 @@ static int snd_microii_spdif_default_update(struct usb_mixer_elem_list *list)
 	u8 reg;
 	int err;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown) {
-		err = -ENODEV;
-		goto end;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
 
 	reg = ((pval >> 4) & 0xf0) | (pval & 0x0f);
 	err = snd_usb_ctl_msg(chip->dev,
@@ -1594,7 +1579,7 @@ static int snd_microii_spdif_default_update(struct usb_mixer_elem_list *list)
 		goto end;
 
  end:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }
 
@@ -1650,11 +1635,9 @@ static int snd_microii_spdif_switch_update(struct usb_mixer_elem_list *list)
 	u8 reg = list->kctl->private_value;
 	int err;
 
-	down_read(&chip->shutdown_rwsem);
-	if (chip->shutdown) {
-		err = -ENODEV;
-		goto end;
-	}
+	err = snd_usb_lock_shutdown(chip);
+	if (err < 0)
+		return err;
 
 	err = snd_usb_ctl_msg(chip->dev,
 			usb_sndctrlpipe(chip->dev, 0),
@@ -1665,8 +1648,7 @@ static int snd_microii_spdif_switch_update(struct usb_mixer_elem_list *list)
 			NULL,
 			0);
 
- end:
-	up_read(&chip->shutdown_rwsem);
+	snd_usb_unlock_shutdown(chip);
 	return err;
 }