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>
diff --git a/sound/usb/card.c b/sound/usb/card.c
index 0450593..b6621bc 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -365,13 +365,15 @@
}
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->usage_count, 0);
+ atomic_set(&chip->shutdown, 0);
chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
le16_to_cpu(dev->descriptor.idProduct));
@@ -495,7 +497,7 @@
mutex_lock(®ister_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;
@@ -585,23 +587,23 @@
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(®ister_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 until all pending tasks done;
+ * they are protected by snd_usb_lock_shutdown()
+ */
+ 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 +633,54 @@
}
}
+/* lock the shutdown (disconnect) task and autoresume */
+int snd_usb_lock_shutdown(struct snd_usb_audio *chip)
+{
+ int err;
+
+ 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;
+}
+
+/* autosuspend and unlock the shutdown */
+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)
{
- int err = -ENODEV;
-
- 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);
-
- return err;
+ if (atomic_read(&chip->shutdown))
+ return -EIO;
+ if (chip->probing)
+ return 0;
+ 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 (chip->probing)
+ return;
+ 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)
@@ -705,7 +733,7 @@
if (--chip->num_suspended_intf)
return 0;
- chip->in_pm = 1;
+ atomic_inc(&chip->active); /* avoid autopm */
/*
* ALSA leaves material resumption to user space
* we just notify and restart the mixers
@@ -725,7 +753,7 @@
chip->autosuspended = 0;
err_out:
- chip->in_pm = 0;
+ atomic_dec(&chip->active); /* allow autopm after this point */
return err;
}
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 03b0744..e6f7189 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -355,8 +355,10 @@
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 @@
{
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 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 c50790c..fd5c49e 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -311,14 +311,11 @@
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 @@
err = -EINVAL;
out:
- up_read(&chip->shutdown_rwsem);
- snd_usb_autosuspend(chip);
+ snd_usb_unlock_shutdown(chip);
return err;
}
@@ -358,21 +354,15 @@
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 @@
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 @@
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 337c317..d3608c0 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -308,11 +308,10 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
goto err;
err:
- up_read(&chip->shutdown_rwsem);
+ snd_usb_unlock_shutdown(chip);
return err;
}
@@ -778,15 +769,14 @@
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 @@
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 @@
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 @@
err = 0;
end:
- up_read(&chip->shutdown_rwsem);
+ snd_usb_unlock_shutdown(chip);
return err;
}
@@ -1562,11 +1549,9 @@
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 @@
goto end;
end:
- up_read(&chip->shutdown_rwsem);
+ snd_usb_unlock_shutdown(chip);
return err;
}
@@ -1650,11 +1635,9 @@
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 @@
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 3079726..cdac517 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -80,7 +80,7 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 5f761ab..0ac89e2 100644
--- a/sound/usb/proc.c
+++ b/sound/usb/proc.c
@@ -46,14 +46,14 @@
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 91d0380..eb1ea71 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -37,11 +37,12 @@
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 +116,7 @@
#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 */