diff options
author | Takashi Iwai <tiwai@suse.de> | 2017-07-06 13:34:40 +0300 |
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committer | Takashi Iwai <tiwai@suse.de> | 2017-07-07 16:34:57 +0300 |
commit | 20e2b791796bd68816fa115f12be5320de2b8021 (patch) | |
tree | 3380b79080ccb2942cd976ddb16f54728e6b1b0f /sound/isa/msnd/msnd_midi.c | |
parent | f33f79f3d0e5caf04dd889cd7cf636261970f009 (diff) | |
download | linux-20e2b791796bd68816fa115f12be5320de2b8021.tar.xz |
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>
Diffstat (limited to 'sound/isa/msnd/msnd_midi.c')
-rw-r--r-- | sound/isa/msnd/msnd_midi.c | 30 |
1 files changed, 15 insertions, 15 deletions
diff --git a/sound/isa/msnd/msnd_midi.c b/sound/isa/msnd/msnd_midi.c index 912b5a9ccbab..013d8d1170fe 100644 --- a/sound/isa/msnd/msnd_midi.c +++ b/sound/isa/msnd/msnd_midi.c @@ -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)); - - 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); + 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, &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); |