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ALSA: msnd: Optimize / harden DSP and MIDI loops 

The ISA msnd drivers have loops fetching the ring-buffer head, tail
and size values inside the loops.  Such codes are inefficient and
fragile.

This patch optimizes it, and also adds the sanity check to avoid the
endless loops.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196131
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196133
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2017-07-06 12:34:40 +02:00
parent f33f79f3d0
commit 20e2b79179
2 changed files with 26 additions and 25 deletions
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28
sound/isa/msnd/msnd_midi.c
View File

@ -120,24 +120,24 @@ void snd_msndmidi_input_read(void *mpuv)
unsigned long flags;
struct snd_msndmidi *mpu = mpuv;
void *pwMIDQData = mpu->dev->mappedbase + MIDQ_DATA_BUFF;
u16 head, tail, size;
spin_lock_irqsave(&mpu->input_lock, flags);
while (readw(mpu->dev->MIDQ + JQS_wTail) !=
readw(mpu->dev->MIDQ + JQS_wHead)) {
u16 wTmp, val;
val = readw(pwMIDQData + 2 * readw(mpu->dev->MIDQ + JQS_wHead));
head = readw(mpu->dev->MIDQ + JQS_wHead);
tail = readw(mpu->dev->MIDQ + JQS_wTail);
size = readw(mpu->dev->MIDQ + JQS_wSize);
if (head > size || tail > size)
goto out;
while (head != tail) {
unsigned char val = readw(pwMIDQData + 2 * head);
if (test_bit(MSNDMIDI_MODE_BIT_INPUT_TRIGGER,
&mpu->mode))
snd_rawmidi_receive(mpu->substream_input,
(unsigned char *)&val, 1);
wTmp = readw(mpu->dev->MIDQ + JQS_wHead) + 1;
if (wTmp > readw(mpu->dev->MIDQ + JQS_wSize))
writew(0, mpu->dev->MIDQ + JQS_wHead);
else
writew(wTmp, mpu->dev->MIDQ + JQS_wHead);
if (test_bit(MSNDMIDI_MODE_BIT_INPUT_TRIGGER, &mpu->mode))
snd_rawmidi_receive(mpu->substream_input, &val, 1);
if (++head > size)
head = 0;
writew(head, mpu->dev->MIDQ + JQS_wHead);
}
out:
spin_unlock_irqrestore(&mpu->input_lock, flags);
}
EXPORT_SYMBOL(snd_msndmidi_input_read);

23
sound/isa/msnd/msnd_pinnacle.c
View File

@ -170,23 +170,24 @@ static irqreturn_t snd_msnd_interrupt(int irq, void *dev_id)
{
struct snd_msnd *chip = dev_id;
void *pwDSPQData = chip->mappedbase + DSPQ_DATA_BUFF;
u16 head, tail, size;
/* Send ack to DSP */
/* inb(chip->io + HP_RXL); */
/* Evaluate queued DSP messages */
while (readw(chip->DSPQ + JQS_wTail) != readw(chip->DSPQ + JQS_wHead)) {
u16 wTmp;
snd_msnd_eval_dsp_msg(chip,
readw(pwDSPQData + 2 * readw(chip->DSPQ + JQS_wHead)));
wTmp = readw(chip->DSPQ + JQS_wHead) + 1;
if (wTmp > readw(chip->DSPQ + JQS_wSize))
writew(0, chip->DSPQ + JQS_wHead);
else
writew(wTmp, chip->DSPQ + JQS_wHead);
head = readw(chip->DSPQ + JQS_wHead);
tail = readw(chip->DSPQ + JQS_wTail);
size = readw(chip->DSPQ + JQS_wSize);
if (head > size || tail > size)
goto out;
while (head != tail) {
snd_msnd_eval_dsp_msg(chip, readw(pwDSPQData + 2 * head));
if (++head > size)
head = 0;
writew(head, chip->DSPQ + JQS_wHead);
}
out:
/* Send ack to DSP */
inb(chip->io + HP_RXL);
return IRQ_HANDLED;