Re: ALSA/usb-audio: snd_usb_autoresume possible recursive locking detected

From: Takashi Iwai
Date: Wed Aug 26 2015 - 04:36:53 EST

On Wed, 26 Aug 2015 09:40:02 +0200,
Alexander Kuleshov wrote:
>
> On 08-25-15, Takashi Iwai wrote:
> > Sorry, a wrong file was attached. Below is the correct one.
>
> I've applied last patch against your for-next tree and seems that
> it brings more problems. I see following messages:
>
> 1. http://pastebin.com/ggC1Nm6X
>
> 2. http://pastebin.com/F4cpyzjm
>
> And moreover some userspace apps hangs and I can't reboot with it
> only hard reset.

Ah, sorry, this was the missing refcount increment at resume.
Below is the revised patch. In the final form, it'll be split to a
few parts, but now it's all folded for ease of testing.


thanks,

Takashi

-- 8< --
From: Takashi Iwai <tiwai@xxxxxxx>
Subject: [PATCH] ALSA: usb-audio: Avoid nested autoresume calls

Since snd_usb_autoresume() invokes down_read() to shutdown_rwsem, this
triggers lockdep warnings 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]

Also, most of these calls are together with another down_read() for
checking the chip->shutdown flag, and it may trigger the similar
lockdep warning, too.

This patch rewrites the logic of snd_usb_autoresume() & co; namely,
- The recursive call of autopm is avoided by the new refcount,
chip->active.
- Instead of rwsem, another refcount, chip->usage_count, is introduced
for tracking the period to delay the shutdown procedure. At
decreasing this refcount, wake_up() to the shutdown waiter is
called.
- 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-by: Alexnader Kuleshov <kuleshovmail@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/usb/card.c | 106 ++++++++++++++++++++-------------------
sound/usb/endpoint.c | 10 ++--
sound/usb/mixer.c | 32 ++++--------
sound/usb/mixer_quirks.c | 126 ++++++++++++++++++++---------------------------
sound/usb/pcm.c | 32 ++++++------
sound/usb/proc.c | 4 +-
sound/usb/usbaudio.h | 12 +++--
7 files changed, 149 insertions(+), 173 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 0450593980fd..80c99fde234b 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -365,13 +365,14 @@ static int snd_usb_audio_create(struct usb_interface *intf,
}

mutex_init(&chip->mutex);
- init_rwsem(&chip->shutdown_rwsem);
+ init_waitqueue_head(&chip->shutdown_wait);
chip->index = idx;
chip->dev = dev;
chip->card = card;
chip->setup = device_setup[idx];
chip->autoclock = autoclock;
- chip->probing = 1;
+ atomic_set(&chip->active, 1); /* avoid autopm during probing */
+ atomic_set(&chip->usage_count, 0);

chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
le16_to_cpu(dev->descriptor.idProduct));
@@ -495,13 +496,13 @@ static int usb_audio_probe(struct usb_interface *intf,
mutex_lock(&register_mutex);
for (i = 0; i < SNDRV_CARDS; i++) {
if (usb_chip[i] && usb_chip[i]->dev == dev) {
- if (usb_chip[i]->shutdown) {
+ if (atomic_read(&usb_chip[i]->shutdown)) {
dev_err(&dev->dev, "USB device is in the shutdown state, cannot create a card instance\n");
err = -EIO;
goto __error;
}
chip = usb_chip[i];
- chip->probing = 1;
+ atomic_inc(&chip->active); /* avoid autopm */
break;
}
}
@@ -561,8 +562,8 @@ static int usb_audio_probe(struct usb_interface *intf,

usb_chip[chip->index] = chip;
chip->num_interfaces++;
- chip->probing = 0;
usb_set_intfdata(intf, chip);
+ atomic_dec(&chip->active);
mutex_unlock(&register_mutex);
return 0;

@@ -570,7 +571,7 @@ static int usb_audio_probe(struct usb_interface *intf,
if (chip) {
if (!chip->num_interfaces)
snd_card_free(chip->card);
- chip->probing = 0;
+ atomic_dec(&chip->active);
}
mutex_unlock(&register_mutex);
return err;
@@ -585,23 +586,20 @@ static void usb_audio_disconnect(struct usb_interface *intf)
struct snd_usb_audio *chip = usb_get_intfdata(intf);
struct snd_card *card;
struct list_head *p;
- bool was_shutdown;

if (chip == (void *)-1L)
return;

card = chip->card;
- down_write(&chip->shutdown_rwsem);
- was_shutdown = chip->shutdown;
- chip->shutdown = 1;
- up_write(&chip->shutdown_rwsem);

mutex_lock(&register_mutex);
- if (!was_shutdown) {
+ if (atomic_inc_return(&chip->shutdown) == 1) {
struct snd_usb_stream *as;
struct snd_usb_endpoint *ep;
struct usb_mixer_interface *mixer;

+ wait_event(chip->shutdown_wait,
+ !atomic_read(&chip->usage_count));
snd_card_disconnect(card);
/* release the pcm resources */
list_for_each_entry(as, &chip->pcm_list, list) {
@@ -631,28 +629,48 @@ static void usb_audio_disconnect(struct usb_interface *intf)
}
}

-#ifdef CONFIG_PM
-
-int snd_usb_autoresume(struct snd_usb_audio *chip)
+int snd_usb_lock_shutdown(struct snd_usb_audio *chip)
{
- int err = -ENODEV;
+ int err;

- down_read(&chip->shutdown_rwsem);
- if (chip->probing || chip->in_pm)
- err = 0;
- else if (!chip->shutdown)
- err = usb_autopm_get_interface(chip->pm_intf);
- up_read(&chip->shutdown_rwsem);
+ atomic_inc(&chip->usage_count);
+ if (atomic_read(&chip->shutdown)) {
+ err = -EIO;
+ goto error;
+ }
+ err = snd_usb_autoresume(chip);
+ if (err < 0)
+ goto error;
+ return 0;

+ error:
+ if (atomic_dec_and_test(&chip->usage_count))
+ wake_up(&chip->shutdown_wait);
return err;
}

+void snd_usb_unlock_shutdown(struct snd_usb_audio *chip)
+{
+ snd_usb_autosuspend(chip);
+ if (atomic_dec_and_test(&chip->usage_count))
+ wake_up(&chip->shutdown_wait);
+}
+
+#ifdef CONFIG_PM
+
+int snd_usb_autoresume(struct snd_usb_audio *chip)
+{
+ if (atomic_read(&chip->shutdown))
+ return -EIO;
+ if (atomic_inc_return(&chip->active) == 1)
+ return usb_autopm_get_interface(chip->pm_intf);
+ return 0;
+}
+
void snd_usb_autosuspend(struct snd_usb_audio *chip)
{
- down_read(&chip->shutdown_rwsem);
- if (!chip->shutdown && !chip->probing && !chip->in_pm)
+ if (atomic_dec_and_test(&chip->active))
usb_autopm_put_interface(chip->pm_intf);
- up_read(&chip->shutdown_rwsem);
}

static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
@@ -665,30 +683,18 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
if (chip == (void *)-1L)
return 0;

- if (!PMSG_IS_AUTO(message)) {
- snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);
- if (!chip->num_suspended_intf++) {
- list_for_each_entry(as, &chip->pcm_list, list) {
- snd_pcm_suspend_all(as->pcm);
- as->substream[0].need_setup_ep =
- as->substream[1].need_setup_ep = true;
- }
- list_for_each(p, &chip->midi_list) {
- snd_usbmidi_suspend(p);
- }
+ snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);
+ if (!chip->num_suspended_intf++) {
+ list_for_each_entry(as, &chip->pcm_list, list) {
+ snd_pcm_suspend_all(as->pcm);
+ as->substream[0].need_setup_ep =
+ as->substream[1].need_setup_ep = true;
}
- } else {
- /*
- * otherwise we keep the rest of the system in the dark
- * to keep this transparent
- */
- if (!chip->num_suspended_intf++)
- chip->autosuspended = 1;
- }
-
- if (chip->num_suspended_intf == 1)
+ list_for_each(p, &chip->midi_list)
+ snd_usbmidi_suspend(p);
list_for_each_entry(mixer, &chip->mixer_list, list)
snd_usb_mixer_suspend(mixer);
+ }

return 0;
}
@@ -705,7 +711,7 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
if (--chip->num_suspended_intf)
return 0;

- chip->in_pm = 1;
+ atomic_inc(&chip->active);
/*
* ALSA leaves material resumption to user space
* we just notify and restart the mixers
@@ -720,12 +726,10 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
snd_usbmidi_resume(p);
}

- if (!chip->autosuspended)
- snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
- chip->autosuspended = 0;
+ snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);

err_out:
- chip->in_pm = 0;
+ atomic_dec(&chip->active);
return err;
}

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 03b074419964..e6f71894ecdc 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -355,8 +355,10 @@ static void snd_complete_urb(struct urb *urb)
if (unlikely(urb->status == -ENOENT || /* unlinked */
urb->status == -ENODEV || /* device removed */
urb->status == -ECONNRESET || /* unlinked */
- urb->status == -ESHUTDOWN || /* device disabled */
- ep->chip->shutdown)) /* device disconnected */
+ urb->status == -ESHUTDOWN)) /* device disabled */
+ goto exit_clear;
+ /* device disconnected */
+ if (unlikely(atomic_read(&ep->chip->shutdown)))
goto exit_clear;

if (usb_pipeout(ep->pipe)) {
@@ -529,7 +531,7 @@ static int deactivate_urbs(struct snd_usb_endpoint *ep, bool force)
{
unsigned int i;

- if (!force && ep->chip->shutdown) /* to be sure... */
+ if (!force && atomic_read(&ep->chip->shutdown)) /* to be sure... */
return -EBADFD;

clear_bit(EP_FLAG_RUNNING, &ep->flags);
@@ -868,7 +870,7 @@ int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, bool can_sleep)
int err;
unsigned int i;

- if (ep->chip->shutdown)
+ if (atomic_read(&ep->chip->shutdown))
return -EBADFD;

/* already running? */
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index c50790cb3f4d..fd5c49e94867 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -311,14 +311,11 @@ static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request,
int timeout = 10;
int idx = 0, err;

- err = snd_usb_autoresume(chip);
+ err = snd_usb_lock_shutdown(chip);
if (err < 0)
return -EIO;

- down_read(&chip->shutdown_rwsem);
while (timeout-- > 0) {
- if (chip->shutdown)
- break;
idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
if (snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), request,
USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
@@ -334,8 +331,7 @@ static int get_ctl_value_v1(struct usb_mixer_elem_info *cval, int request,
err = -EINVAL;

out:
- up_read(&chip->shutdown_rwsem);
- snd_usb_autosuspend(chip);
+ snd_usb_unlock_shutdown(chip);
return err;
}

@@ -358,21 +354,15 @@ static int get_ctl_value_v2(struct usb_mixer_elem_info *cval, int request,

memset(buf, 0, sizeof(buf));

- ret = snd_usb_autoresume(chip) ? -EIO : 0;
+ ret = snd_usb_lock_shutdown(chip) ? -EIO : 0;
if (ret)
goto error;

- down_read(&chip->shutdown_rwsem);
- if (chip->shutdown) {
- ret = -ENODEV;
- } else {
- idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
- ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
+ idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
+ ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0), bRequest,
USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
validx, idx, buf, size);
- }
- up_read(&chip->shutdown_rwsem);
- snd_usb_autosuspend(chip);
+ snd_usb_unlock_shutdown(chip);

if (ret < 0) {
error:
@@ -485,13 +475,12 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
buf[1] = (value_set >> 8) & 0xff;
buf[2] = (value_set >> 16) & 0xff;
buf[3] = (value_set >> 24) & 0xff;
- err = snd_usb_autoresume(chip);
+
+ err = snd_usb_lock_shutdown(chip);
if (err < 0)
return -EIO;
- down_read(&chip->shutdown_rwsem);
+
while (timeout-- > 0) {
- if (chip->shutdown)
- break;
idx = snd_usb_ctrl_intf(chip) | (cval->head.id << 8);
if (snd_usb_ctl_msg(chip->dev,
usb_sndctrlpipe(chip->dev, 0), request,
@@ -506,8 +495,7 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval,
err = -EINVAL;

out:
- up_read(&chip->shutdown_rwsem);
- snd_usb_autosuspend(chip);
+ snd_usb_unlock_shutdown(chip);
return err;
}

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;
}

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 30797269d5aa..cdac5179db3f 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -80,7 +80,7 @@ static snd_pcm_uframes_t snd_usb_pcm_pointer(struct snd_pcm_substream *substream
unsigned int hwptr_done;

subs = (struct snd_usb_substream *)substream->runtime->private_data;
- if (subs->stream->chip->shutdown)
+ if (atomic_read(&subs->stream->chip->shutdown))
return SNDRV_PCM_POS_XRUN;
spin_lock(&subs->lock);
hwptr_done = subs->hwptr_done;
@@ -735,12 +735,11 @@ static int snd_usb_hw_params(struct snd_pcm_substream *substream,
return -EINVAL;
}

- down_read(&subs->stream->chip->shutdown_rwsem);
- if (subs->stream->chip->shutdown)
- ret = -ENODEV;
- else
- ret = set_format(subs, fmt);
- up_read(&subs->stream->chip->shutdown_rwsem);
+ ret = snd_usb_lock_shutdown(subs->stream->chip);
+ if (ret < 0)
+ return ret;
+ ret = set_format(subs, fmt);
+ snd_usb_unlock_shutdown(subs->stream->chip);
if (ret < 0)
return ret;

@@ -763,13 +762,12 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
subs->cur_audiofmt = NULL;
subs->cur_rate = 0;
subs->period_bytes = 0;
- down_read(&subs->stream->chip->shutdown_rwsem);
- if (!subs->stream->chip->shutdown) {
+ if (!snd_usb_lock_shutdown(subs->stream->chip)) {
stop_endpoints(subs, true);
snd_usb_endpoint_deactivate(subs->sync_endpoint);
snd_usb_endpoint_deactivate(subs->data_endpoint);
+ snd_usb_unlock_shutdown(subs->stream->chip);
}
- up_read(&subs->stream->chip->shutdown_rwsem);
return snd_pcm_lib_free_vmalloc_buffer(substream);
}

@@ -791,11 +789,9 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
return -ENXIO;
}

- down_read(&subs->stream->chip->shutdown_rwsem);
- if (subs->stream->chip->shutdown) {
- ret = -ENODEV;
- goto unlock;
- }
+ ret = snd_usb_lock_shutdown(subs->stream->chip);
+ if (ret < 0)
+ return ret;
if (snd_BUG_ON(!subs->data_endpoint)) {
ret = -EIO;
goto unlock;
@@ -844,7 +840,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
ret = start_endpoints(subs, true);

unlock:
- up_read(&subs->stream->chip->shutdown_rwsem);
+ snd_usb_unlock_shutdown(subs->stream->chip);
return ret;
}

@@ -1246,9 +1242,11 @@ static int snd_usb_pcm_close(struct snd_pcm_substream *substream, int direction)

stop_endpoints(subs, true);

- if (!as->chip->shutdown && subs->interface >= 0) {
+ if (subs->interface >= 0 &&
+ !snd_usb_lock_shutdown(subs->stream->chip)) {
usb_set_interface(subs->dev, subs->interface, 0);
subs->interface = -1;
+ snd_usb_unlock_shutdown(subs->stream->chip);
}

subs->pcm_substream = NULL;
diff --git a/sound/usb/proc.c b/sound/usb/proc.c
index 5f761ab34c01..0ac89e294d31 100644
--- a/sound/usb/proc.c
+++ b/sound/usb/proc.c
@@ -46,14 +46,14 @@ static inline unsigned get_high_speed_hz(unsigned int usb_rate)
static void proc_audio_usbbus_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
{
struct snd_usb_audio *chip = entry->private_data;
- if (!chip->shutdown)
+ if (!atomic_read(&chip->shutdown))
snd_iprintf(buffer, "%03d/%03d\n", chip->dev->bus->busnum, chip->dev->devnum);
}

static void proc_audio_usbid_read(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
{
struct snd_usb_audio *chip = entry->private_data;
- if (!chip->shutdown)
+ if (!atomic_read(&chip->shutdown))
snd_iprintf(buffer, "%04x:%04x\n",
USB_ID_VENDOR(chip->usb_id),
USB_ID_PRODUCT(chip->usb_id));
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 91d0380431b4..46cf8d14415f 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -37,11 +37,10 @@ struct snd_usb_audio {
struct usb_interface *pm_intf;
u32 usb_id;
struct mutex mutex;
- struct rw_semaphore shutdown_rwsem;
- unsigned int shutdown:1;
- unsigned int probing:1;
- unsigned int in_pm:1;
- unsigned int autosuspended:1;
+ atomic_t active;
+ atomic_t shutdown;
+ atomic_t usage_count;
+ wait_queue_head_t shutdown_wait;
unsigned int txfr_quirk:1; /* Subframe boundaries on transfers */

int num_interfaces;
@@ -115,4 +114,7 @@ struct snd_usb_audio_quirk {
#define combine_triple(s) (combine_word(s) | ((unsigned int)(s)[2] << 16))
#define combine_quad(s) (combine_triple(s) | ((unsigned int)(s)[3] << 24))

+int snd_usb_lock_shutdown(struct snd_usb_audio *chip);
+void snd_usb_unlock_shutdown(struct snd_usb_audio *chip);
+
#endif /* __USBAUDIO_H */
--
2.5.0

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