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ALSA: seq: virmidi: Use READ_ONCE/WRITE_ONCE() macros

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The trigger flag in vmidi object can be referred in different contexts
concurrently, hence it's better to be put with READ_ONCE() and
WRITE_ONCE() macros to assure the accesses.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2018-07-30 14:48:29 +02:00
parent f7debfe540
commit 89b4ab213f
2 changed files with 6 additions and 10 deletions
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2
include/sound/seq_virmidi.h
View file

@ -36,7 +36,7 @@ struct snd_virmidi {
int seq_mode;
int client;
int port;
unsigned int trigger: 1;
bool trigger;
struct snd_midi_event *parser;
struct snd_seq_event event;
struct snd_virmidi_dev *rdev;

14
sound/core/seq/seq_virmidi.c
View file

@ -89,7 +89,7 @@ static int snd_virmidi_dev_receive_event(struct snd_virmidi_dev *rdev,
else
down_read(&rdev->filelist_sem);
list_for_each_entry(vmidi, &rdev->filelist, list) {
if (!vmidi->trigger)
if (!READ_ONCE(vmidi->trigger))
continue;
if (ev->type == SNDRV_SEQ_EVENT_SYSEX) {
if ((ev->flags & SNDRV_SEQ_EVENT_LENGTH_MASK) != SNDRV_SEQ_EVENT_LENGTH_VARIABLE)
@ -147,11 +147,7 @@ static void snd_virmidi_input_trigger(struct snd_rawmidi_substream *substream, i
{
struct snd_virmidi *vmidi = substream->runtime->private_data;
if (up) {
vmidi->trigger = 1;
} else {
vmidi->trigger = 0;
}
WRITE_ONCE(vmidi->trigger, !!up);
}
/* process rawmidi bytes and send events;
@ -175,7 +171,7 @@ static void snd_vmidi_output_work(struct work_struct *work)
return;
}
while (vmidi->trigger) {
while (READ_ONCE(vmidi->trigger)) {
if (snd_rawmidi_transmit(substream, &input, 1) != 1)
break;
if (snd_midi_event_encode_byte(vmidi->parser, input,
@ -201,7 +197,7 @@ static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream,
{
struct snd_virmidi *vmidi = substream->runtime->private_data;
vmidi->trigger = !!up;
WRITE_ONCE(vmidi->trigger, !!up);
if (up)
queue_work(system_highpri_wq, &vmidi->output_work);
}
@ -289,7 +285,7 @@ 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 */
WRITE_ONCE(vmidi->trigger, false); /* to be sure */
cancel_work_sync(&vmidi->output_work);
snd_midi_event_free(vmidi->parser);
substream->runtime->private_data = NULL;