Re: [PATCH] qv4l2: Prevent high CPU usage on device disconnect

[Tasos Sahanidis]

Signed-off-by: Tasos Sahanidis <ta...@tasossah.com>

On 2019-05-27 15:20, Hans Verkuil wrote:
> Hi Tasos,
> 
> On 5/9/19 3:32 PM, Tasos Sahanidis wrote:
>> On device disconnect, ApplicationWindow::ctrlEvent() gets called
>> continuously, causing high CPU usage.
>> Closing the device handles once ENODEV is returned fixes this.
> 
> I'm missing your Signed-of-by. Can you reply to this and add your SoB so I
> can merge this patch?
> 
> Regards,
> 
>       Hans
> 
>> ---
>>  utils/qv4l2/alsa_stream.c |  2 +-
>>  utils/qv4l2/qv4l2.cpp     | 24 +++++++++++++++++++-----
>>  2 files changed, 20 insertions(+), 6 deletions(-)
>>
>> diff --git a/utils/qv4l2/alsa_stream.c b/utils/qv4l2/alsa_stream.c
>> index 05944822..2dca283b 100644
>> --- a/utils/qv4l2/alsa_stream.c
>> +++ b/utils/qv4l2/alsa_stream.c
>> @@ -433,7 +433,7 @@ static snd_pcm_sframes_t readbuf(snd_pcm_t *handle, char 
>> *buf, long len)
>>      snd_pcm_uframes_t frames;
>>      snd_pcm_htimestamp(handle, &frames, &timestamp);
>>      r = snd_pcm_readi(handle, buf, len);
>> -    if (r < 0 && r != -EAGAIN) {
>> +    if (r < 0 && !(r == -EAGAIN || r == -ENODEV)) {
>>      r = snd_pcm_recover(handle, r, 0);
>>      if (r < 0)
>>          fprintf(error_fp, "alsa: overrun recover error: %s\n", 
>> snd_strerror(r));
>> diff --git a/utils/qv4l2/qv4l2.cpp b/utils/qv4l2/qv4l2.cpp
>> index b52a3b60..9ac2c332 100644
>> --- a/utils/qv4l2/qv4l2.cpp
>> +++ b/utils/qv4l2/qv4l2.cpp
>> @@ -495,8 +495,9 @@ void ApplicationWindow::setAudioBufferSize()
>>  void ApplicationWindow::ctrlEvent()
>>  {
>>      v4l2_event ev;
>> +    int event_ret = 0;
>>  
>> -    while (dqevent(ev) == 0) {
>> +    while ((event_ret = dqevent(ev)) == 0) {
>>              if (ev.type == V4L2_EVENT_SOURCE_CHANGE) {
>>                      m_genTab->sourceChange(ev);
>>                      continue;
>> @@ -551,6 +552,15 @@ void ApplicationWindow::ctrlEvent()
>>                      setString(ev.id, c.string);
>>              free(c.string);
>>      }
>> +
>> +    if (event_ret && errno == ENODEV) {
>> +            closeDevice();
>> +            if (m_capture != NULL) {
>> +                    m_capture->stop();
>> +                    delete m_capture;
>> +                    m_capture = NULL;
>> +            }
>> +    }
>>  }
>>  
>>  void ApplicationWindow::newCaptureWin()
>> @@ -558,6 +568,7 @@ void ApplicationWindow::newCaptureWin()
>>      if (m_capture != NULL) {
>>              m_capture->stop();
>>              delete m_capture;
>> +            m_capture = NULL;
>>      }
>>  
>>      switch (m_renderMethod) {
>> @@ -1135,7 +1146,7 @@ void ApplicationWindow::stopStreaming()
>>      if (!m_genTab->isSDR() && m_genTab->isRadio())
>>              return;
>>  
>> -    if (v4l_type_is_capture(g_type()))
>> +    if (v4l_type_is_capture(g_type()) && m_capture != NULL)
>>              m_capture->stop();
>>  
>>      m_snapshotAct->setDisabled(true);
>> @@ -1561,8 +1572,10 @@ void ApplicationWindow::makeFullScreen(bool checked)
>>  void ApplicationWindow::closeDevice()
>>  {
>>      stopAudio();
>> -    delete m_sigMapper;
>> -    m_sigMapper = NULL;
>> +    if(m_sigMapper != NULL) {
>> +            m_sigMapper->deleteLater();
>> +            m_sigMapper = NULL;
>> +    }
>>      m_capStartAct->setEnabled(false);
>>      m_capStartAct->setChecked(false);
>>      m_capStepAct->setEnabled(false);
>> @@ -1579,7 +1592,7 @@ void ApplicationWindow::closeDevice()
>>                      m_outNotifier = NULL;
>>              }
>>              if (m_ctrlNotifier) {
>> -                    delete m_ctrlNotifier;
>> +                    m_ctrlNotifier->deleteLater();
>>                      m_ctrlNotifier = NULL;
>>              }
>>              delete [] m_frameData;
>> @@ -1740,6 +1753,7 @@ void ApplicationWindow::closeEvent(QCloseEvent *event)
>>  {
>>      closeDevice();
>>      delete m_capture;
>> +    m_capture = NULL;
>>      event->accept();
>>  }
>>  
>>
>