[mythtv] mythbackend spinning in "Waiting for a thread ..."

Robert Tsai rtsai1111 at comcast.net
Thu Jun 16 13:47:12 UTC 2005

When using mythweb to see the "Recorded Programs" page, the
mythbackend process always ends up stuck in MainServer::readSocket,
continuously logging "Waiting for a thread ...".

I've seen previous references to this spinning in the mailing list
archives as far back as February, but no resolution, and those
messages did not include any system specifics. I myself have not been
able to reproduce this problem until very recently, but I just went
through a complete system rebuild, so I there are too many variables
changing to identify anything as a "cause". In February/March (when I
had no problems) I was running a version of debian pure64. Now I am
running Ubuntu Hoary (clean install).

As mentioned in the archives, this requires a restart of mythbackend.

As far as I can tell, the only way for this to stop (gracefully) is
for ProcessRequestThread::run() to eventually call

This was not reproducible when there was a small number of recordings
(I am going to go out on a limb and say "5", since that happens to be
the number of threads created by the MainServer object). But now I
have 10 recordings and can consistently reproduce this problem by
clicking on "Recorded Programs". I don't experience a problem with any
other mythweb pages.

I am going to blindly hypothesize that this might be related to the
AMD64-specific pthreads problem for which exists Kyle's workaround in
RingBuffer, but there don't appear to be any readwrite locks involved
in this bit of the code (although I'm not familiar with QMutex).

My system characteristics:

	- AMD64
	- Ubuntu Hoary
	- MythTV CVS (last night)

I'd like to know whether or not any other users currently see this
problems (and please provide CPU/distribution specifics). Please reply
offlist; I'll accumulate responses and summarize if there is any

Any other hints would be appreciated.

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