[mythtv-commits] Ticket #10732: Recordings fail after upgrade to .25

[MythTV]

#10732: Recordings fail after upgrade to .25
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 Reporter:  daveshome@…           |          Owner:  danielk
     Type:  Bug Report - General  |         Status:  assigned
 Priority:  minor                 |      Milestone:  unknown
Component:  MythTV - Recording    |        Version:  0.25-fixes
 Severity:  medium                |     Resolution:
 Keywords:                        |  Ticket locked:  0
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Comment (by ltskinol@…):

 Patch attached.

 Changes libs/libmythtv/DeviceReadBuffer.cpp ::Poll as follows:

 - Reorganizes main loop to be clearer, without changing functionality.
 - Always check return from poll() before using the return structures.
 This was a bug, though perhaps innocuous.
 - Adds missing lock before setting error=true.  This was a bug.
 - Treats a poll() return of POLLHUP as EOF rather than an error.

 The last change is what "fixes" the problem.  What's happening is that
 the ivtv driver returns HUP when an attempt to read at EOF of the
 stream.  Myth was then interpreting this as an error, and
 re-initializing the driver, which wasn't the correct behavior.

 Works for me to fix the problem noted in the bug.

 I say "fixes" because I think this is just a workaround for a race
 condition, but I don't know enough about Myth to debug that.  What I
 see in the logs is:

 2012-10-03 00:05:15.375429 I [9918/9932] TVRecEvent tv_rec.cpp:1029
 (HandleStateChange) - TVRec(4): Changing from RecordingOnly to None
 2012-10-03 00:05:15.690488 E [9918/10107] DeviceReadBuffer
 DeviceReadBuffer.cpp:490 (Poll) - DevRdB(/dev/video0): poll eof
 (POLLHUP)
 2012-10-03 00:05:16.039436 E [9918/10105] RecThread
 mpegrecorder.cpp:1017 (run) - MPEGRec(/dev/video0): Device EOF
 detected
 2012-10-03 00:05:16.200041 I [9918/9918] CoreContext scheduler.cpp:638
 (UpdateRecStatus) - Updating status for Seinfeld:"The Revenge" on card
 id 4 (Recording => Recorded)

 At the end of a recording, I usually see one of these POLLHUP errors,
 indicating that the Poll() loop read from the device and got an EOF
 indication.  My theory is that Myth is stopping the recording (and
 somehow indicating to ivtv that it needs to stop encoding) but then
 has no way of stopping an in-progress system poll() call.  So the
 poll() returns POLLHUP, indicating that the encoder has gone away.
 Seems like the proper fix is to somehow cancel the poll().  My "fix"
 just works around the problem by not treating POLLHUP as an error.

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Ticket URL: <http://code.mythtv.org/trac/ticket/10732#comment:33>
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