ALSA: pcm_lib - optimize wake_up() calls for PCM I/O

As noted by pl bossart <bossart.nospam@gmail.com>, the PCM I/O routines
(snd_pcm_lib_write1, snd_pcm_lib_read1) should block wake_up() calls
until all samples are not processed.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

3 files changed, 27 insertions, 12 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index fe1b131842be..e26fb3c58037 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -311,6 +311,7 @@ struct snd_pcm_runtime {
         struct snd_pcm_mmap_control *control;
 
         /* -- locking / scheduling -- */
+        unsigned int nowake: 1;         /* no wakeup (data-copy in progress) */
         wait_queue_head_t sleep;
         struct fasync_struct *fasync;
 
@@ -839,6 +840,8 @@ void snd_pcm_set_sync(struct snd_pcm_substream *substream);
 int snd_pcm_lib_interleave_len(struct snd_pcm_substream *substream);
 int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
                       unsigned int cmd, void *arg);                      
+int snd_pcm_update_state(struct snd_pcm_substream *substream,
+                         struct snd_pcm_runtime *runtime);
 int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream);
 int snd_pcm_playback_xrun_check(struct snd_pcm_substream *substream);
 int snd_pcm_capture_xrun_check(struct snd_pcm_substream *substream);
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 70a4f7428d78..a63226232ef4 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -263,8 +263,8 @@ static void xrun_log_show(struct snd_pcm_substream *substream)
 
 #endif
 
-static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
-                                      struct snd_pcm_runtime *runtime)
+int snd_pcm_update_state(struct snd_pcm_substream *substream,
+                         struct snd_pcm_runtime *runtime)
 {
         snd_pcm_uframes_t avail;
 
@@ -285,7 +285,7 @@ static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
                         return -EPIPE;
                 }
         }
-        if (avail >= runtime->control->avail_min)
+        if (!runtime->nowake && avail >= runtime->control->avail_min)
                 wake_up(&runtime->sleep);
         return 0;
 }
@@ -441,7 +441,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
         if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
                 snd_pcm_gettime(runtime, (struct timespec *)&runtime->status->tstamp);
 
-        return snd_pcm_update_hw_ptr_post(substream, runtime);
+        return snd_pcm_update_state(substream, runtime);
 }
 
 /* CAUTION: call it with irq disabled */
@@ -1792,6 +1792,7 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
                 goto _end_unlock;
         }
 
+        runtime->nowake = 1;
         while (size > 0) {
                 snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
                 snd_pcm_uframes_t avail;
@@ -1813,15 +1814,17 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
                 if (frames > cont)
                         frames = cont;
                 if (snd_BUG_ON(!frames)) {
+                        runtime->nowake = 0;
                         snd_pcm_stream_unlock_irq(substream);
                         return -EINVAL;
                 }
                 appl_ptr = runtime->control->appl_ptr;
                 appl_ofs = appl_ptr % runtime->buffer_size;
                 snd_pcm_stream_unlock_irq(substream);
-                if ((err = transfer(substream, appl_ofs, data, offset, frames)) < 0)
-                        goto _end;
+                err = transfer(substream, appl_ofs, data, offset, frames);
                 snd_pcm_stream_lock_irq(substream);
+                if (err < 0)
+                        goto _end_unlock;
                 switch (runtime->status->state) {
                 case SNDRV_PCM_STATE_XRUN:
                         err = -EPIPE;
@@ -1850,8 +1853,10 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
                 }
         }
  _end_unlock:
+        runtime->nowake = 0;
+        if (xfer > 0 && err >= 0)
+                snd_pcm_update_state(substream, runtime);
         snd_pcm_stream_unlock_irq(substream);
- _end:
         return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
 }
 
@@ -2009,6 +2014,7 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
                 goto _end_unlock;
         }
 
+        runtime->nowake = 1;
         while (size > 0) {
                 snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
                 snd_pcm_uframes_t avail;
@@ -2037,15 +2043,17 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
                 if (frames > cont)
                         frames = cont;
                 if (snd_BUG_ON(!frames)) {
+                        runtime->nowake = 0;
                         snd_pcm_stream_unlock_irq(substream);
                         return -EINVAL;
                 }
                 appl_ptr = runtime->control->appl_ptr;
                 appl_ofs = appl_ptr % runtime->buffer_size;
                 snd_pcm_stream_unlock_irq(substream);
-                if ((err = transfer(substream, appl_ofs, data, offset, frames)) < 0)
-                        goto _end;
+                err = transfer(substream, appl_ofs, data, offset, frames);
                 snd_pcm_stream_lock_irq(substream);
+                if (err < 0)
+                        goto _end_unlock;
                 switch (runtime->status->state) {
                 case SNDRV_PCM_STATE_XRUN:
                         err = -EPIPE;
@@ -2068,8 +2076,10 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
                 xfer += frames;
         }
  _end_unlock:
+        runtime->nowake = 0;
+        if (xfer > 0 && err >= 0)
+                snd_pcm_update_state(substream, runtime);
         snd_pcm_stream_unlock_irq(substream);
- _end:
         return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
 }
 
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 8e777f71717c..27284f628361 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -516,6 +516,7 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
                              struct snd_pcm_sw_params *params)
 {
         struct snd_pcm_runtime *runtime;
+        int err;
 
         if (PCM_RUNTIME_CHECK(substream))
                 return -ENXIO;
@@ -540,6 +541,7 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
                 if (params->silence_threshold > runtime->buffer_size)
                         return -EINVAL;
         }
+        err = 0;
         snd_pcm_stream_lock_irq(substream);
         runtime->tstamp_mode = params->tstamp_mode;
         runtime->period_step = params->period_step;
@@ -553,10 +555,10 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
                 if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
                     runtime->silence_size > 0)
                         snd_pcm_playback_silence(substream, ULONG_MAX);
-                wake_up(&runtime->sleep);
+                err = snd_pcm_update_state(substream, runtime);
         }
         snd_pcm_stream_unlock_irq(substream);
-        return 0;
+        return err;
 }
 
 static int snd_pcm_sw_params_user(struct snd_pcm_substream *substream,