[5/6] alsa-lib:pcm: check state before enter poll on timer.

Commit Message

[e-mail] Dec. 30, 2016, 6:29 a.m. UTC

From: Andreas Pape <[e-mail]>

To avoid the chances of timeout, we need to check the enter poll
in state xrun.

Signed-off-by: Andreas Pape <[e-mail]>

Patch

diff --git a/src/pcm/pcm_direct.c b/src/pcm/pcm_direct.c
index 779845c..2928512 100644
--- a/src/pcm/pcm_direct.c
+++ b/src/pcm/pcm_direct.c
@@ -549,6 +549,42 @@  int snd_pcm_direct_timer_stop(snd_pcm_direct_t *dmix)
 	snd_timer_stop(dmix->timer);
 	return 0;
 }
+/*
+ * This is the only operation guaranteed to be called before entering poll().
+ * Direct plugins use fd of snd_timer to poll on, these timers do NOT check state of substream in kernel by intention.
+ * Only the enter to xrun might be notified once (SND_TIMER_EVENT_MSTOP).
+ * If xrun event was not correctly handled or was ignored it will never be evaluated again afterwards.
+ * This will result in snd_pcm_wait() always returning timeout.
+ * In contrast poll() on pcm hardware checks ALSA state and will immediately return POLLERR on XRUN.
+ *
+ * To prevent timeout and applications endlessly spinning without xrun detected we add a state check
+ * here which may trigger the xrun sequence.
+ *
+ * return count of filled descriptors or negative error code
+ */
+int snd_pcm_direct_poll_descriptors(snd_pcm_t *pcm, struct pollfd *pfds, unsigned int space)
+{
+	if (pcm->poll_fd < 0) {
+		SNDMSG("poll_fd < 0");
+		return -EIO;
+	}
+	if (space >= 1 && pfds) {
+		pfds->fd = pcm->poll_fd;
+		pfds->events = pcm->poll_events | POLLERR | POLLNVAL;
+	} else {
+		return 0;
+	}
+
+	/*this will also evaluate slave state and enter xrun if necessary*/
+	switch (snd_pcm_state(pcm)) {
+	case SND_PCM_STATE_XRUN:
+		return -EPIPE;
+	default:
+		break;
+	}
+	return 1;
+}
+
 
 int snd_pcm_direct_poll_revents(snd_pcm_t *pcm, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
 {
diff --git a/src/pcm/pcm_direct.h b/src/pcm/pcm_direct.h
index 569d2be..3a1c1c0 100644
--- a/src/pcm/pcm_direct.h
+++ b/src/pcm/pcm_direct.h
@@ -301,6 +301,7 @@  int snd_pcm_direct_parse_bindings(snd_pcm_direct_t *dmix,
 				  snd_config_t *cfg);
 int snd_pcm_direct_nonblock(snd_pcm_t *pcm, int nonblock);
 int snd_pcm_direct_async(snd_pcm_t *pcm, int sig, pid_t pid);
+int snd_pcm_direct_poll_descriptors(snd_pcm_t *pcm, struct pollfd *pfds, unsigned int space);
 int snd_pcm_direct_poll_revents(snd_pcm_t *pcm, struct pollfd *pfds, unsigned int nfds, unsigned short *revents);
 int snd_pcm_direct_info(snd_pcm_t *pcm, snd_pcm_info_t * info);
 int snd_pcm_direct_hw_refine(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index 5c3eb2d..320c948 100644
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -463,17 +463,23 @@  static int snd_pcm_dmix_sync_ptr(snd_pcm_t *pcm)
 static snd_pcm_state_t snd_pcm_dmix_state(snd_pcm_t *pcm)
 {
 	snd_pcm_direct_t *dmix = pcm->private_data;
+	int err;
 	snd_pcm_state_t state;
 	state = snd_pcm_state(dmix->spcm);
 	switch (state) {
-	case SND_PCM_STATE_XRUN:
 	case SND_PCM_STATE_SUSPENDED:
 	case SND_PCM_STATE_DISCONNECTED:
 		dmix->state = state;
 		return state;
+	case SND_PCM_STATE_XRUN:
+		if ((err = snd_pcm_direct_slave_recover(dmix)) < 0)
+			return err;
+		break;
 	default:
 		break;
 	}
+	snd_pcm_direct_client_chk_xrun(dmix, pcm);
+
 	if (dmix->state == STATE_RUN_PENDING)
 		return SNDRV_PCM_STATE_RUNNING;
 	return dmix->state;
@@ -969,7 +975,7 @@  static const snd_pcm_fast_ops_t snd_pcm_dmix_fast_ops = {
 	.avail_update = snd_pcm_dmix_avail_update,
 	.mmap_commit = snd_pcm_dmix_mmap_commit,
 	.htimestamp = snd_pcm_dmix_htimestamp,
-	.poll_descriptors = NULL,
+	.poll_descriptors = snd_pcm_direct_poll_descriptors,
 	.poll_descriptors_count = NULL,
 	.poll_revents = snd_pcm_dmix_poll_revents,
 };
diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c
index 707e2c2..f4fa32b 100644
--- a/src/pcm/pcm_dshare.c
+++ b/src/pcm/pcm_dshare.c
@@ -255,17 +255,22 @@  static int snd_pcm_dshare_status(snd_pcm_t *pcm, snd_pcm_status_t * status)
 static snd_pcm_state_t snd_pcm_dshare_state(snd_pcm_t *pcm)
 {
 	snd_pcm_direct_t *dshare = pcm->private_data;
+	int err;
 	snd_pcm_state_t state;
 	state = snd_pcm_state(dshare->spcm);
 	switch (state) {
-	case SND_PCM_STATE_XRUN:
 	case SND_PCM_STATE_SUSPENDED:
 	case SND_PCM_STATE_DISCONNECTED:
 		dshare->state = state;
 		return state;
+	case SND_PCM_STATE_XRUN:
+		if ((err = snd_pcm_direct_slave_recover(dshare)) < 0)
+			return err;
+		break;
 	default:
 		break;
 	}
+	snd_pcm_direct_client_chk_xrun(dshare, pcm);
 	if (dshare->state == STATE_RUN_PENDING)
 		return SNDRV_PCM_STATE_RUNNING;
 	return dshare->state;
@@ -646,7 +651,7 @@  static const snd_pcm_fast_ops_t snd_pcm_dshare_fast_ops = {
 	.avail_update = snd_pcm_dshare_avail_update,
 	.mmap_commit = snd_pcm_dshare_mmap_commit,
 	.htimestamp = snd_pcm_dshare_htimestamp,
-	.poll_descriptors = NULL,
+	.poll_descriptors = snd_pcm_direct_poll_descriptors,
 	.poll_descriptors_count = NULL,
 	.poll_revents = snd_pcm_direct_poll_revents,
 };
diff --git a/src/pcm/pcm_dsnoop.c b/src/pcm/pcm_dsnoop.c
index 512e957..0729a5a 100644
--- a/src/pcm/pcm_dsnoop.c
+++ b/src/pcm/pcm_dsnoop.c
@@ -208,17 +208,22 @@  static int snd_pcm_dsnoop_status(snd_pcm_t *pcm, snd_pcm_status_t * status)
 static snd_pcm_state_t snd_pcm_dsnoop_state(snd_pcm_t *pcm)
 {
 	snd_pcm_direct_t *dsnoop = pcm->private_data;
+	int err;
 	snd_pcm_state_t state;
 	state = snd_pcm_state(dsnoop->spcm);
 	switch (state) {
-	case SND_PCM_STATE_XRUN:
 	case SND_PCM_STATE_SUSPENDED:
 	case SND_PCM_STATE_DISCONNECTED:
 		dsnoop->state = state;
 		return state;
+	case SND_PCM_STATE_XRUN:
+		if ((err = snd_pcm_direct_slave_recover(dsnoop)) < 0)
+			return err;
+		break;
 	default:
 		break;
 	}
+	snd_pcm_direct_client_chk_xrun(dsnoop, pcm);
 	return dsnoop->state;
 }
 
@@ -531,7 +536,7 @@  static const snd_pcm_fast_ops_t snd_pcm_dsnoop_fast_ops = {
 	.avail_update = snd_pcm_dsnoop_avail_update,
 	.mmap_commit = snd_pcm_dsnoop_mmap_commit,
 	.htimestamp = snd_pcm_dsnoop_htimestamp,
-	.poll_descriptors = NULL,
+	.poll_descriptors = snd_pcm_direct_poll_descriptors,
 	.poll_descriptors_count = NULL,
 	.poll_revents = snd_pcm_direct_poll_revents,
 };