I did test the patch and while it doesn't seem to introduce any
negative side effects it does not provide a remedy for the original
problem that was seen after introducing
9d659ae14b545c4296e812c70493bfdc999b5c1c (you probably did not expect
that either).
Cheers,
-olli
On 27 April 2018 at 18:33, Mauro Carvalho Chehab
<mchehab+samsung@xxxxxxxxxx> wrote:
> Em Fri, 27 Apr 2018 16:25:08 +0200
> Olli Salonen <olli.salonen@xxxxxx> escreveu:
>
>> Thanks for the suggestion Antti.
>>
>> I've tried to add a delay in various places, but haven't seen any
>> improvement. However, what I did saw was that if I added an msleep
>> after the lock:
>>
>> static int dvbsky_usb_generic_rw(struct dvb_usb_device *d,
>> u8 *wbuf, u16 wlen, u8 *rbuf, u16 rlen)
>> {
>> int ret;
>> struct dvbsky_state *state = d_to_priv(d);
>>
>> mutex_lock(&d->usb_mutex);
>> msleep(20);
>>
>> The error was seen very within a minute. If I increased the msleep to
>> 50, it failed within seconds. This doesn't seem to make sense to me.
>> This is the only function where usb_mutex is used. If the mutex is
>> held for a longer time, the next attempt to lock the mutex should just
>> be delayed a bit, no?
>
> I don't like the idea of having two mutexes there to protect reading/writing
> to data one for "generic" r/w ops, and another one just for streaming
> control, with ends by calling the "generic" mutex.
>
> IMHO, I would get rid of one of the mutexes, e. g. something like the
> patch below (untested).
>
> Regards,
> Mauro
>
> media: dvbsky: use just one mutex for serializing device R/W ops
>
> Right now, there are two mutexes serializing r/w ops: one "generic"
> and another one specifically for stream on/off.
>
> Clean it a little bit, getting rid of one of the mutexes.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
>
> diff --git a/drivers/media/usb/dvb-usb-v2/dvbsky.c b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> index 43eb82884555..50553975c39d 100644
> --- a/drivers/media/usb/dvb-usb-v2/dvbsky.c
> +++ b/drivers/media/usb/dvb-usb-v2/dvbsky.c
> @@ -31,7 +31,6 @@ MODULE_PARM_DESC(disable_rc, "Disable inbuilt IR receiver.");
> DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
>
> struct dvbsky_state {
> - struct mutex stream_mutex;
> u8 ibuf[DVBSKY_BUF_LEN];
> u8 obuf[DVBSKY_BUF_LEN];
> u8 last_lock;
> @@ -68,18 +67,17 @@ static int dvbsky_usb_generic_rw(struct dvb_usb_device *d,
>
> static int dvbsky_stream_ctrl(struct dvb_usb_device *d, u8 onoff)
> {
> - struct dvbsky_state *state = d_to_priv(d);
> int ret;
> - u8 obuf_pre[3] = { 0x37, 0, 0 };
> - u8 obuf_post[3] = { 0x36, 3, 0 };
> + static u8 obuf_pre[3] = { 0x37, 0, 0 };
> + static u8 obuf_post[3] = { 0x36, 3, 0 };
>
> - mutex_lock(&state->stream_mutex);
> - ret = dvbsky_usb_generic_rw(d, obuf_pre, 3, NULL, 0);
> + mutex_lock(&d->usb_mutex);
> + ret = dvb_usbv2_generic_rw_locked(d, obuf_pre, 3, NULL, 0);
> if (!ret && onoff) {
> msleep(20);
> - ret = dvbsky_usb_generic_rw(d, obuf_post, 3, NULL, 0);
> + ret = dvb_usbv2_generic_rw_locked(d, obuf_post, 3, NULL, 0);
> }
> - mutex_unlock(&state->stream_mutex);
> + mutex_unlock(&d->usb_mutex);
> return ret;
> }
>
> @@ -744,8 +742,6 @@ static int dvbsky_init(struct dvb_usb_device *d)
> if (ret)
> return ret;
> */
> - mutex_init(&state->stream_mutex);
> -
> state->last_lock = 0;
>
> return 0;
>
>
>
> Thanks,
> Mauro
