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authorTakashi Iwai <tiwai@suse.de>2018-07-29 23:03:05 +0200
committerTakashi Iwai <tiwai@suse.de>2018-07-30 14:51:51 +0200
commitf7debfe54090d1a1c38e1f070be20d83bb70a8e0 (patch)
tree6718f64cfde2c98b7a3d596784a49b754beba3f7 /sound/core
parent16c796e8fac353d736055322ca6a38ba3c49f5e2 (diff)
downloadlinux-f7debfe54090d1a1c38e1f070be20d83bb70a8e0.tar.bz2
ALSA: seq: virmidi: Offload the output event processing
The virmidi sequencer stuff tries to translate the rawmidi bytes to sequencer events and deliver the packets at trigger callback. The amount of the whole process of these translations and deliveries depends on the incoming rawmidi bytes, and we have no limit for that; this was the cause of a CPU soft lockup that had been reported and fixed recently. Although we've fixed the soft lockup by putting the temporary unlock and cond_resched(), it's rather a quick band aid. In this patch, meanwhile, the event parsing and delivery process is offloaded to a dedicated work, and the trigger callback just kicks it off. It has three merits, at least: - The processing is always done in a sleepable context, which can assure the event delivery with non-atomic flag without hackish is_atomic() usage. - Other relevant codes can be simplified, reducing the lines - It makes me happier Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core')
-rw-r--r--sound/core/seq/seq_virmidi.c100
1 files changed, 46 insertions, 54 deletions
diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c
index 8ebbca554e99..67ea5d62cebc 100644
--- a/sound/core/seq/seq_virmidi.c
+++ b/sound/core/seq/seq_virmidi.c
@@ -154,71 +154,59 @@ static void snd_virmidi_input_trigger(struct snd_rawmidi_substream *substream, i
}
}
-/*
- * trigger rawmidi stream for output
+/* process rawmidi bytes and send events;
+ * we need no lock here for vmidi->event since it's handled only in this work
*/
-static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream, int up)
+static void snd_vmidi_output_work(struct work_struct *work)
{
- struct snd_virmidi *vmidi = substream->runtime->private_data;
- int count, res;
- unsigned char buf[32], *pbuf;
- unsigned long flags;
- bool check_resched = !in_atomic();
+ struct snd_virmidi *vmidi;
+ struct snd_rawmidi_substream *substream;
+ unsigned char input;
+ int ret;
+
+ vmidi = container_of(work, struct snd_virmidi, output_work);
+ substream = vmidi->substream;
+
+ /* discard the outputs in dispatch mode unless subscribed */
+ if (vmidi->seq_mode == SNDRV_VIRMIDI_SEQ_DISPATCH &&
+ !(vmidi->rdev->flags & SNDRV_VIRMIDI_SUBSCRIBE)) {
+ while (!snd_rawmidi_transmit_empty(substream))
+ snd_rawmidi_transmit_ack(substream, 1);
+ return;
+ }
- if (up) {
- vmidi->trigger = 1;
- if (vmidi->seq_mode == SNDRV_VIRMIDI_SEQ_DISPATCH &&
- !(vmidi->rdev->flags & SNDRV_VIRMIDI_SUBSCRIBE)) {
- while (snd_rawmidi_transmit(substream, buf,
- sizeof(buf)) > 0) {
- /* ignored */
- }
- return;
- }
- spin_lock_irqsave(&substream->runtime->lock, flags);
+ while (vmidi->trigger) {
+ if (snd_rawmidi_transmit(substream, &input, 1) != 1)
+ break;
+ if (snd_midi_event_encode_byte(vmidi->parser, input,
+ &vmidi->event) <= 0)
+ continue;
if (vmidi->event.type != SNDRV_SEQ_EVENT_NONE) {
- if (snd_seq_kernel_client_dispatch(vmidi->client, &vmidi->event, in_atomic(), 0) < 0)
- goto out;
+ ret = snd_seq_kernel_client_dispatch(vmidi->client,
+ &vmidi->event,
+ false, 0);
vmidi->event.type = SNDRV_SEQ_EVENT_NONE;
- }
- while (1) {
- count = __snd_rawmidi_transmit_peek(substream, buf, sizeof(buf));
- if (count <= 0)
+ if (ret < 0)
break;
- pbuf = buf;
- while (count > 0) {
- res = snd_midi_event_encode(vmidi->parser, pbuf, count, &vmidi->event);
- if (res < 0) {
- snd_midi_event_reset_encode(vmidi->parser);
- continue;
- }
- __snd_rawmidi_transmit_ack(substream, res);
- pbuf += res;
- count -= res;
- if (vmidi->event.type != SNDRV_SEQ_EVENT_NONE) {
- if (snd_seq_kernel_client_dispatch(vmidi->client, &vmidi->event, in_atomic(), 0) < 0)
- goto out;
- vmidi->event.type = SNDRV_SEQ_EVENT_NONE;
- }
- }
- if (!check_resched)
- continue;
- /* do temporary unlock & cond_resched() for avoiding
- * CPU soft lockup, which may happen via a write from
- * a huge rawmidi buffer
- */
- spin_unlock_irqrestore(&substream->runtime->lock, flags);
- cond_resched();
- spin_lock_irqsave(&substream->runtime->lock, flags);
}
- out:
- spin_unlock_irqrestore(&substream->runtime->lock, flags);
- } else {
- vmidi->trigger = 0;
+ /* rawmidi input might be huge, allow to have a break */
+ cond_resched();
}
}
/*
+ * trigger rawmidi stream for output
+ */
+static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+ struct snd_virmidi *vmidi = substream->runtime->private_data;
+
+ vmidi->trigger = !!up;
+ if (up)
+ queue_work(system_highpri_wq, &vmidi->output_work);
+}
+
+/*
* open rawmidi handle for input
*/
static int snd_virmidi_input_open(struct snd_rawmidi_substream *substream)
@@ -270,6 +258,7 @@ static int snd_virmidi_output_open(struct snd_rawmidi_substream *substream)
vmidi->port = rdev->port;
snd_virmidi_init_event(vmidi, &vmidi->event);
vmidi->rdev = rdev;
+ INIT_WORK(&vmidi->output_work, snd_vmidi_output_work);
runtime->private_data = vmidi;
return 0;
}
@@ -299,6 +288,9 @@ static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream)
static int snd_virmidi_output_close(struct snd_rawmidi_substream *substream)
{
struct snd_virmidi *vmidi = substream->runtime->private_data;
+
+ vmidi->trigger = 0; /* to be sure */
+ cancel_work_sync(&vmidi->output_work);
snd_midi_event_free(vmidi->parser);
substream->runtime->private_data = NULL;
kfree(vmidi);