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Ticket #10970: Mythbackend failed recordings, deadlocks

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Aug 3, 2012, 4:08 AM

Post #1 of 8 (145 views)
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Ticket #10970: Mythbackend failed recordings, deadlocks

#10970: Mythbackend failed recordings, deadlocks
-------------------------------------+-------------------------------------
Reporter: Peter Townsend | Type: Bug Report -
<elpinkus@…> | General
Status: new | Priority: minor
Milestone: unknown | Component: MythTV - General
Version: Master Head | Severity: medium
Keywords: | Ticket locked: 0
-------------------------------------+-------------------------------------
In the last week or so, my backend has been getting into a state where all
recordings fail to start. Killing mythbackend and running it again makes
things record again for a day or two.

This afternoon two recordings failed to start and mythbackend stopped
responding through mythweb or the internal webserver.

I followed the instructions on the wiki for attaching gdb and generating a
backtrace. Let me know what other information I can provide.

Running version v0.26-alpha-79-gb379de3. Possibly related to #10870.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10970>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Aug 3, 2012, 10:49 AM

Post #2 of 8 (135 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

noreply at mythtv

Aug 3, 2012, 12:15 PM

Post #3 of 8 (134 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

#10970: Mythbackend failed recordings, deadlocks
-----------------------------------------+--------------------------------
Reporter: Peter Townsend <elpinkus@…> | Owner:
Type: Bug Report - General | Status: infoneeded_new
Priority: minor | Milestone: unknown
Component: MythTV - General | Version: Master Head
Severity: medium | Resolution:
Keywords: | Ticket locked: 0
-----------------------------------------+--------------------------------

Comment (by Daniel Thor Kristjansson <danielk@…>):

In [changeset:9f0be65bfcf192191d8905012f173f80a19f66d5/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="9f0be65bfcf192191d8905012f173f80a19f66d5"
Refs #10970. Don't print EOF as error if it's expected.

This isn't the cause of any issues, it's just a bit confusing when reading
the logs.
When we close a DRB we are expecting a EOF so it's not an error when we
see it..
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10970#comment:2>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Aug 3, 2012, 1:55 PM

Post #4 of 8 (135 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

#10970: Mythbackend failed recordings, deadlocks
-----------------------------------------+--------------------------------
Reporter: Peter Townsend <elpinkus@…> | Owner:
Type: Bug Report - General | Status: infoneeded_new
Priority: minor | Milestone: unknown
Component: MythTV - General | Version: Master Head
Severity: medium | Resolution:
Keywords: | Ticket locked: 0
-----------------------------------------+--------------------------------

Comment (by danielk):

As far as I can tell this shouldn't be happening.

StreamHandler::Start() seems to be waiting for the thread to start. It's
waiting for either _running or _error to be set. I don't see any way that
DVBStreamHandler::run() can exit without setting either of those. It also
seems like DVBStreamHandler::RunTS() is running a piece of code that would
only be run after setting _running to true, however that could be in
service of another stream. It is possible that MTHread::start() has called
QThread::start(), but the thread was never started because we ran out of
memory or we exceeded our process allocation. However, that shouldn't
occur with any normally configured Linux system. Finally, while _running
is not declared as volatile, the while loop that checks it calls a
function outside the current translation unit so gcc should not optimise
the check away since it can't know that _running isn't set by that call.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10970#comment:3>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Aug 3, 2012, 2:13 PM

Post #5 of 8 (135 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

noreply at mythtv

Aug 3, 2012, 2:50 PM

Post #6 of 8 (133 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

#10970: Mythbackend failed recordings, deadlocks
-------------------------------------+-------------------------------------
Reporter: Peter Townsend | Owner: Daniel Kristjansson
<elpinkus@…> | <danielk@…>
Type: Bug Report - General | Status: closed
Priority: minor | Milestone: unknown
Component: MythTV - General | Version: Master Head
Severity: medium | Resolution: fixed
Keywords: | Ticket locked: 0
-------------------------------------+-------------------------------------
Changes (by Daniel Kristjansson <danielk@…>):

* owner: => Daniel Kristjansson <danielk@…>
* status: infoneeded_new => closed
* resolution: => fixed

Comment:

In [changeset:7d01e691d2bb58ed7dcbbdcca93ec06dc3a7381b/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="7d01e691d2bb58ed7dcbbdcca93ec06dc3a7381b"
Fixes #10970. Fix StreamHandler restart race.

We wait for _running to be set to false, but we need the thread to be
in the finish state or QThread::start() will exit silently without
starting the thread. Since we're calling QThread::wait() we don't
really need the while (_running) loop at all in either Start() or
Stop(), so I've removed it. This race probably dates back to the
pthread->QThread porting.
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10970#comment:5>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Aug 3, 2012, 2:58 PM

Post #7 of 8 (131 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

noreply at mythtv

Oct 1, 2012, 9:43 AM

Post #8 of 8 (42 views)
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Re: Ticket #10970: Mythbackend failed recordings, deadlocks [In reply to]

#10970: Mythbackend failed recordings, deadlocks
-------------------------------------+-------------------------------------
Reporter: Peter Townsend | Owner: Daniel Kristjansson
<elpinkus@…> | <danielk@…>
Type: Bug Report - General | Status: closed
Priority: minor | Milestone: 0.26
Component: MythTV - General | Version: Master Head
Severity: medium | Resolution: fixed
Keywords: | Ticket locked: 0
-------------------------------------+-------------------------------------

Comment (by Daniel Kristjansson <danielk@…>):

In [changeset:eb52783e9f7ad232cbf4afb22dbc604898514e45/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="eb52783e9f7ad232cbf4afb22dbc604898514e45"
Fixes #10970. Fix StreamHandler restart race.

We wait for _running to be set to false, but we need the thread to be
in the finish state or QThread::start() will exit silently without
starting the thread. Since we're calling QThread::wait() we don't
really need the while (_running) loop at all in either Start() or
Stop(), so I've removed it. This race probably dates back to the
pthread->QThread porting.
(cherry picked from commit 7d01e691d2bb58ed7dcbbdcca93ec06dc3a7381b)
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10970#comment:7>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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