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Re: [Qemu-devel] [PATCH v2 52/52] usbaudio: change playback counters to
From: |
Kővágó Zoltán |
Subject: |
Re: [Qemu-devel] [PATCH v2 52/52] usbaudio: change playback counters to 64 bit |
Date: |
Thu, 27 Dec 2018 23:08:52 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
Hi,
On 2018-12-25 11:50, Philippe Mathieu-Daudé wrote:
> On 12/23/18 9:52 PM, Kővágó, Zoltán wrote:
>> With stereo playback, they need about 375 minutes of continuous audio
>> playback to overflow, which is usually not a problem (as stopping and
>> later resuming playback resets the counters). But with 7.1 audio, they
>> only need about 95 minutes to overflow.
>>
>> After the overflow, the buf->prod % USBAUDIO_PACKET_SIZE(channels)
>> assertion no longer holds true, which will result in overflowing the
>> buffer. With 64 bit variables, it would take about 762000 years to
>> overflow.
>>
>> Signed-off-by: Kővágó, Zoltán <address@hidden>
>> ---
>> hw/usb/dev-audio.c | 12 +++++++-----
>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/usb/dev-audio.c b/hw/usb/dev-audio.c
>> index 29475a2b70..45ffc3ebb3 100644
>> --- a/hw/usb/dev-audio.c
>> +++ b/hw/usb/dev-audio.c
>> @@ -577,9 +577,9 @@ static const USBDesc desc_audio_multi = {
>>
>> struct streambuf {
>> uint8_t *data;
>> - uint32_t size;
>> - uint32_t prod;
>> - uint32_t cons;
>> + size_t size;
>> + uint64_t prod;
>> + uint64_t cons;
>
> OK.
>
>> };
>>
>> static void streambuf_init(struct streambuf *buf, uint32_t size,
>> @@ -600,12 +600,14 @@ static void streambuf_fini(struct streambuf *buf)
>>
>> static int streambuf_put(struct streambuf *buf, USBPacket *p, uint32_t
>> channels)
>> {
>> - uint32_t free = buf->size - (buf->prod - buf->cons);
>> + uint64_t free = buf->size - (buf->prod - buf->cons);
>
> I'd use ssize_t here.
>
Hm, I agree with the signed part, but I'm not sure about the size_t
part. Granted, there's a big problem if buf->prod - buf->cons can't be
representated on 32 bits, but still I'd rather use int64_t in this case
and prevent this potential truncation on 32-bit platforms.
>>
>> if (free < USBAUDIO_PACKET_SIZE(channels)) {
>> return 0;
>> }
>>
>> + /* can happen if prod overflows */
>> + assert(buf->prod % USBAUDIO_PACKET_SIZE(channels) == 0);
>> usb_packet_copy(p, buf->data + (buf->prod % buf->size),
>> USBAUDIO_PACKET_SIZE(channels));
>> buf->prod += USBAUDIO_PACKET_SIZE(channels);
>> @@ -614,7 +616,7 @@ static int streambuf_put(struct streambuf *buf,
>> USBPacket *p, uint32_t channels)
>>
>> static uint8_t *streambuf_get(struct streambuf *buf, size_t *len)
>> {
>> - uint32_t used = buf->prod - buf->cons;
>> + uint64_t used = buf->prod - buf->cons;
>> uint8_t *data;
>>
>> if (!used) {
>
> Eventually here:
>
> ssize_t used = buf->prod - buf->cons;
>
> if (used <= 0) {
> return NULL;
> }
>
Regards,
Zoltan
- [Qemu-devel] [PATCH v2 41/52] audio: common rate control code for timer based outputs, (continued)
- [Qemu-devel] [PATCH v2 41/52] audio: common rate control code for timer based outputs, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 29/52] alsaaudio: port to the new audio backend api, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 34/52] paaudio: port to the new audio backend api, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 42/52] audio: split ctl_* functions into enable_* and volume_*, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 47/52] audio: replace shift in audio_pcm_info with bytes_per_frame, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 43/52] audio: add mixeng option (documentation), Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 50/52] usb-audio: do not count on avail bytes actually available, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 49/52] paaudio: channel-map option, Kővágó, Zoltán, 2018/12/23
- [Qemu-devel] [PATCH v2 52/52] usbaudio: change playback counters to 64 bit, Kővágó, Zoltán, 2018/12/23
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Philippe Mathieu-Daudé, 2018/12/25
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Programmingkid, 2018/12/26
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Kővágó Zoltán, 2018/12/27
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Programmingkid, 2018/12/27
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Kővágó Zoltán, 2018/12/28
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Programmingkid, 2018/12/28
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Zoltán Kővágó, 2018/12/28
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Programmingkid, 2018/12/28
- Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Kővágó Zoltán, 2018/12/31
Re: [Qemu-devel] [PATCH v2 00/52] Audio 5.1 patches, Philippe Mathieu-Daudé, 2018/12/27