diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index e1c747c70883757d61183b67ff6e2c315a1cac70..3bde24575a99aa54c5d9827ef92abafa47db845f 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -30,6 +30,7 @@
#include <linux/mm.h>
#include <linux/bitops.h>
#include <linux/pm_qos.h>
+#include <linux/refcount.h>
#define snd_pcm_substream_chip(substream) ((substream)->private_data)
#define snd_pcm_chip(pcm) ((pcm)->private_data)
@@ -439,6 +440,7 @@ struct snd_pcm_group { /* keep linked substreams */
spinlock_t lock;
struct mutex mutex;
struct list_head substreams;
+ refcount_t refs;
};
struct pid;
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index fb45386270d5a1523ccb43f7e1f32a60dd33f344..cbde23fc67a9b9930bc8249ee24d40b50eb79c09 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -85,7 +85,6 @@ static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream);
*
*/
-static DEFINE_RWLOCK(snd_pcm_link_rwlock);
static DECLARE_RWSEM(snd_pcm_link_rwsem);
/* Writer in rwsem may block readers even during its waiting in queue,
@@ -105,8 +104,24 @@ void snd_pcm_group_init(struct snd_pcm_group *group)
spin_lock_init(&group->lock);
mutex_init(&group->mutex);
INIT_LIST_HEAD(&group->substreams);
+ refcount_set(&group->refs, 0);
}
+/* define group lock helpers */
+#define DEFINE_PCM_GROUP_LOCK(action, mutex_action) \
+static void snd_pcm_group_ ## action(struct snd_pcm_group *group, bool nonatomic) \
+{ \
+ if (nonatomic) \
+ mutex_ ## mutex_action(&group->mutex); \
+ else \
+ spin_ ## action(&group->lock); \
+}
+
+DEFINE_PCM_GROUP_LOCK(lock, lock);
+DEFINE_PCM_GROUP_LOCK(unlock, unlock);
+DEFINE_PCM_GROUP_LOCK(lock_irq, lock);
+DEFINE_PCM_GROUP_LOCK(unlock_irq, unlock);
+
#define PCM_LOCK_DEFAULT 0
#define PCM_LOCK_IRQ 1
#define PCM_LOCK_IRQSAVE 2
@@ -116,21 +131,19 @@ static unsigned long __snd_pcm_stream_lock_mode(struct snd_pcm_substream *substr
{
unsigned long flags = 0;
if (substream->pcm->nonatomic) {
- down_read_nested(&snd_pcm_link_rwsem, SINGLE_DEPTH_NESTING);
mutex_lock(&substream->self_group.mutex);
} else {
switch (mode) {
case PCM_LOCK_DEFAULT:
- read_lock(&snd_pcm_link_rwlock);
+ spin_lock(&substream->self_group.lock);
break;
case PCM_LOCK_IRQ:
- read_lock_irq(&snd_pcm_link_rwlock);
+ spin_lock_irq(&substream->self_group.lock);
break;
case PCM_LOCK_IRQSAVE:
- read_lock_irqsave(&snd_pcm_link_rwlock, flags);
+ spin_lock_irqsave(&substream->self_group.lock, flags);
break;
}
- spin_lock(&substream->self_group.lock);
}
return flags;
}
@@ -140,19 +153,16 @@ static void __snd_pcm_stream_unlock_mode(struct snd_pcm_substream *substream,
{
if (substream->pcm->nonatomic) {
mutex_unlock(&substream->self_group.mutex);
- up_read(&snd_pcm_link_rwsem);
} else {
- spin_unlock(&substream->self_group.lock);
-
switch (mode) {
case PCM_LOCK_DEFAULT:
- read_unlock(&snd_pcm_link_rwlock);
+ spin_unlock(&substream->self_group.lock);
break;
case PCM_LOCK_IRQ:
- read_unlock_irq(&snd_pcm_link_rwlock);
+ spin_unlock_irq(&substream->self_group.lock);
break;
case PCM_LOCK_IRQSAVE:
- read_unlock_irqrestore(&snd_pcm_link_rwlock, flags);
+ spin_unlock_irqrestore(&substream->self_group.lock, flags);
break;
}
}
@@ -1138,6 +1148,61 @@ static void snd_pcm_group_assign(struct snd_pcm_substream *substream,
list_move(&substream->link_list, &new_group->substreams);
}
+/*
+ * Unref and unlock the group, but keep the stream lock;
+ * when the group becomes empty and no longer referred, destroy itself
+ */
+static void snd_pcm_group_unref(struct snd_pcm_group *group,
+ struct snd_pcm_substream *substream)
+{
+ bool do_free;
+
+ if (!group)
+ return;
+ do_free = refcount_dec_and_test(&group->refs) &&
+ list_empty(&group->substreams);
+ snd_pcm_group_unlock(group, substream->pcm->nonatomic);
+ if (do_free)
+ kfree(group);
+}
+
+/*
+ * Lock the group inside a stream lock and reference it;
+ * return the locked group object, or NULL if not linked
+ */
+static struct snd_pcm_group *
+snd_pcm_stream_group_ref(struct snd_pcm_substream *substream)
+{
+ bool nonatomic = substream->pcm->nonatomic;
+ struct snd_pcm_group *group;
+ bool trylock;
+
+ for (;;) {
+ if (!snd_pcm_stream_linked(substream))
+ return NULL;
+ group = substream->group;
+ /* block freeing the group object */
+ refcount_inc(&group->refs);
+
+ trylock = nonatomic ? mutex_trylock(&group->mutex) :
+ spin_trylock(&group->lock);
+ if (trylock)
+ break; /* OK */
+
+ /* re-lock for avoiding ABBA deadlock */
+ snd_pcm_stream_unlock(substream);
+ snd_pcm_group_lock(group, nonatomic);
+ snd_pcm_stream_lock(substream);
+
+ /* check the group again; the above opens a small race window */
+ if (substream->group == group)
+ break; /* OK */
+ /* group changed, try again */
+ snd_pcm_group_unref(group, substream);
+ }
+ return group;
+}
+
/*
* Note: call with stream lock
*/
@@ -1145,28 +1210,15 @@ static int snd_pcm_action(const struct action_ops *ops,
struct snd_pcm_substream *substream,
int state)
{
+ struct snd_pcm_group *group;
int res;
- if (!snd_pcm_stream_linked(substream))
- return snd_pcm_action_single(ops, substream, state);
-
- if (substream->pcm->nonatomic) {
- if (!mutex_trylock(&substream->group->mutex)) {
- mutex_unlock(&substream->self_group.mutex);
- mutex_lock(&substream->group->mutex);
- mutex_lock(&substream->self_group.mutex);
- }
+ group = snd_pcm_stream_group_ref(substream);
+ if (group)
res = snd_pcm_action_group(ops, substream, state, 1);
- mutex_unlock(&substream->group->mutex);
- } else {
- if (!spin_trylock(&substream->group->lock)) {
- spin_unlock(&substream->self_group.lock);
- spin_lock(&substream->group->lock);
- spin_lock(&substream->self_group.lock);
- }
- res = snd_pcm_action_group(ops, substream, state, 1);
- spin_unlock(&substream->group->lock);
- }
+ else
+ res = snd_pcm_action_single(ops, substream, state);
+ snd_pcm_group_unref(group, substream);
return res;
}
@@ -1193,6 +1245,7 @@ static int snd_pcm_action_nonatomic(const struct action_ops *ops,
{
int res;
+ /* Guarantee the group members won't change during non-atomic action */
down_read(&snd_pcm_link_rwsem);
if (snd_pcm_stream_linked(substream))
res = snd_pcm_action_group(ops, substream, state, 0);
@@ -1821,6 +1874,7 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
struct snd_card *card;
struct snd_pcm_runtime *runtime;
struct snd_pcm_substream *s;
+ struct snd_pcm_group *group;
wait_queue_entry_t wait;
int result = 0;
int nonblock = 0;
@@ -1837,7 +1891,6 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
} else if (substream->f_flags & O_NONBLOCK)
nonblock = 1;
- down_read(&snd_pcm_link_rwsem);
snd_pcm_stream_lock_irq(substream);
/* resume pause */
if (runtime->status->state == SNDRV_PCM_STATE_PAUSED)
@@ -1862,6 +1915,7 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
}
/* find a substream to drain */
to_check = NULL;
+ group = snd_pcm_stream_group_ref(substream);
snd_pcm_group_for_each_entry(s, substream) {
if (s->stream != SNDRV_PCM_STREAM_PLAYBACK)
continue;
@@ -1871,12 +1925,12 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
break;
}
}
+ snd_pcm_group_unref(group, substream);
if (!to_check)
break; /* all drained */
init_waitqueue_entry(&wait, current);
add_wait_queue(&to_check->sleep, &wait);
snd_pcm_stream_unlock_irq(substream);
- up_read(&snd_pcm_link_rwsem);
if (runtime->no_period_wakeup)
tout = MAX_SCHEDULE_TIMEOUT;
else {
@@ -1888,9 +1942,17 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
tout = msecs_to_jiffies(tout * 1000);
}
tout = schedule_timeout_interruptible(tout);
- down_read(&snd_pcm_link_rwsem);
+
snd_pcm_stream_lock_irq(substream);
- remove_wait_queue(&to_check->sleep, &wait);
+ group = snd_pcm_stream_group_ref(substream);
+ snd_pcm_group_for_each_entry(s, substream) {
+ if (s->runtime == to_check) {
+ remove_wait_queue(&to_check->sleep, &wait);
+ break;
+ }
+ }
+ snd_pcm_group_unref(group, substream);
+
if (card->shutdown) {
result = -ENODEV;
break;
@@ -1910,7 +1972,6 @@ static int snd_pcm_drain(struct snd_pcm_substream *substream,
unlock:
snd_pcm_stream_unlock_irq(substream);
- up_read(&snd_pcm_link_rwsem);
return result;
}
@@ -1972,7 +2033,8 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
int res = 0;
struct snd_pcm_file *pcm_file;
struct snd_pcm_substream *substream1;
- struct snd_pcm_group *group;
+ struct snd_pcm_group *group, *target_group;
+ bool nonatomic = substream->pcm->nonatomic;
struct fd f = fdget(fd);
if (!f.file)
@@ -1989,8 +2051,8 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
goto _nolock;
}
snd_pcm_group_init(group);
+
down_write_nonfifo(&snd_pcm_link_rwsem);
- write_lock_irq(&snd_pcm_link_rwlock);
if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN ||
substream->runtime->status->state != substream1->runtime->status->state ||
substream->pcm->nonatomic != substream1->pcm->nonatomic) {
@@ -2001,13 +2063,21 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
res = -EALREADY;
goto _end;
}
+
+ snd_pcm_stream_lock_irq(substream);
if (!snd_pcm_stream_linked(substream)) {
snd_pcm_group_assign(substream, group);
- group = NULL;
+ group = NULL; /* assigned, don't free this one below */
}
- snd_pcm_group_assign(substream1, substream->group);
+ target_group = substream->group;
+ snd_pcm_stream_unlock_irq(substream);
+
+ snd_pcm_group_lock_irq(target_group, nonatomic);
+ snd_pcm_stream_lock(substream1);
+ snd_pcm_group_assign(substream1, target_group);
+ snd_pcm_stream_unlock(substream1);
+ snd_pcm_group_unlock_irq(target_group, nonatomic);
_end:
- write_unlock_irq(&snd_pcm_link_rwlock);
up_write(&snd_pcm_link_rwsem);
_nolock:
kfree(group);
@@ -2018,22 +2088,27 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
static void relink_to_local(struct snd_pcm_substream *substream)
{
+ snd_pcm_stream_lock(substream);
snd_pcm_group_assign(substream, &substream->self_group);
+ snd_pcm_stream_unlock(substream);
}
static int snd_pcm_unlink(struct snd_pcm_substream *substream)
{
struct snd_pcm_group *group;
+ bool nonatomic = substream->pcm->nonatomic;
+ bool do_free = false;
int res = 0;
down_write_nonfifo(&snd_pcm_link_rwsem);
- write_lock_irq(&snd_pcm_link_rwlock);
+
if (!snd_pcm_stream_linked(substream)) {
res = -EALREADY;
goto _end;
}
group = substream->group;
+ snd_pcm_group_lock_irq(group, nonatomic);
relink_to_local(substream);
@@ -2042,11 +2117,14 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream)
relink_to_local(list_first_entry(&group->substreams,
struct snd_pcm_substream,
link_list));
- kfree(group);
+ do_free = !refcount_read(&group->refs);
}
+ snd_pcm_group_unlock_irq(group, nonatomic);
+ if (do_free)
+ kfree(group);
+
_end:
- write_unlock_irq(&snd_pcm_link_rwlock);
up_write(&snd_pcm_link_rwsem);
return res;
}