[mythtv] mythmusic mutex problem with latest cvs

Andy McMullan andymcm at gmail.com
Thu Jan 27 18:30:51 EST 2005


Upgraded to latest CVS today, and my mythmusic is broken. (I last
updated a week or two ago, so must be a recent change). The problem is
that the first song starts playing ok, but when I select a second
song, the UI hangs (the original song keeps playing).

The UI is blocked waiting on the decoder mutex in PlaybackBox::stop():

    if (decoder && decoder->running())
    {
        decoder->mutex()->lock();   // BLOCKED HERE

Meanwhile the decoder thread continues to acquire and release the
mutex quite happily.

Coming from a Windows background, this behaviour seems odd. I'd expect
the UI thread to get a run before the decoder thread could acquire the
mutex again (assuming equal thread priorities). Doing some research on
linux mutexes, it seems things are a bit different - here is someone
reporting a similar problem:
https://listman.redhat.com/archives/phil-list/2004-February/msg00003.html.
Unfortunately the responses are inconclusive. One guy says this
starvation is to be expected, another says it's not. Like the poster,
I'm using fedora core 1.

Any ideas?

Andy


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