diff options
Diffstat (limited to 'sound/core/pcm_native.c')
| -rw-r--r-- | sound/core/pcm_native.c | 69 |
1 files changed, 67 insertions, 2 deletions
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index bb4297d12066..9dddcf59fe0c 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -77,6 +77,26 @@ 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, + * and this may lead to a deadlock when the code path takes read sem + * twice (e.g. one in snd_pcm_action_nonatomic() and another in + * snd_pcm_stream_lock()). As a (suboptimal) workaround, let writer to + * spin until it gets the lock. + */ +static inline void down_write_nonblock(struct rw_semaphore *lock) +{ + while (!down_write_trylock(lock)) + cond_resched(); +} + +/** + * snd_pcm_stream_lock - Lock the PCM stream + * @substream: PCM substream + * + * This locks the PCM stream's spinlock or mutex depending on the nonatomic + * flag of the given substream. This also takes the global link rw lock + * (or rw sem), too, for avoiding the race with linked streams. + */ void snd_pcm_stream_lock(struct snd_pcm_substream *substream) { if (substream->pcm->nonatomic) { @@ -89,6 +109,12 @@ void snd_pcm_stream_lock(struct snd_pcm_substream *substream) } EXPORT_SYMBOL_GPL(snd_pcm_stream_lock); +/** + * snd_pcm_stream_lock - Unlock the PCM stream + * @substream: PCM substream + * + * This unlocks the PCM stream that has been locked via snd_pcm_stream_lock(). + */ void snd_pcm_stream_unlock(struct snd_pcm_substream *substream) { if (substream->pcm->nonatomic) { @@ -101,6 +127,14 @@ void snd_pcm_stream_unlock(struct snd_pcm_substream *substream) } EXPORT_SYMBOL_GPL(snd_pcm_stream_unlock); +/** + * snd_pcm_stream_lock_irq - Lock the PCM stream + * @substream: PCM substream + * + * This locks the PCM stream like snd_pcm_stream_lock() and disables the local + * IRQ (only when nonatomic is false). In nonatomic case, this is identical + * as snd_pcm_stream_lock(). + */ void snd_pcm_stream_lock_irq(struct snd_pcm_substream *substream) { if (!substream->pcm->nonatomic) @@ -109,6 +143,12 @@ void snd_pcm_stream_lock_irq(struct snd_pcm_substream *substream) } EXPORT_SYMBOL_GPL(snd_pcm_stream_lock_irq); +/** + * snd_pcm_stream_unlock_irq - Unlock the PCM stream + * @substream: PCM substream + * + * This is a counter-part of snd_pcm_stream_lock_irq(). + */ void snd_pcm_stream_unlock_irq(struct snd_pcm_substream *substream) { snd_pcm_stream_unlock(substream); @@ -127,6 +167,13 @@ unsigned long _snd_pcm_stream_lock_irqsave(struct snd_pcm_substream *substream) } EXPORT_SYMBOL_GPL(_snd_pcm_stream_lock_irqsave); +/** + * snd_pcm_stream_unlock_irqrestore - Unlock the PCM stream + * @substream: PCM substream + * @flags: irq flags + * + * This is a counter-part of snd_pcm_stream_lock_irqsave(). + */ void snd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream *substream, unsigned long flags) { @@ -1747,7 +1794,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) res = -ENOMEM; goto _nolock; } - down_write(&snd_pcm_link_rwsem); + down_write_nonblock(&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 || @@ -1794,7 +1841,7 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream) struct snd_pcm_substream *s; int res = 0; - down_write(&snd_pcm_link_rwsem); + down_write_nonblock(&snd_pcm_link_rwsem); write_lock_irq(&snd_pcm_link_rwlock); if (!snd_pcm_stream_linked(substream)) { res = -EALREADY; @@ -3319,6 +3366,15 @@ static const struct vm_operations_struct snd_pcm_vm_ops_data_fault = { /* * mmap the DMA buffer on RAM */ + +/** + * snd_pcm_lib_default_mmap - Default PCM data mmap function + * @substream: PCM substream + * @area: VMA + * + * This is the default mmap handler for PCM data. When mmap pcm_ops is NULL, + * this function is invoked implicitly. + */ int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream, struct vm_area_struct *area) { @@ -3354,6 +3410,15 @@ EXPORT_SYMBOL_GPL(snd_pcm_lib_default_mmap); * mmap the DMA buffer on I/O memory area */ #if SNDRV_PCM_INFO_MMAP_IOMEM +/** + * snd_pcm_lib_mmap_iomem - Default PCM data mmap function for I/O mem + * @substream: PCM substream + * @area: VMA + * + * When your hardware uses the iomapped pages as the hardware buffer and + * wants to mmap it, pass this function as mmap pcm_ops. Note that this + * is supposed to work only on limited architectures. + */ int snd_pcm_lib_mmap_iomem(struct snd_pcm_substream *substream, struct vm_area_struct *area) { |