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

[Hans Verkuil]

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();
>  }
>  
>