Mailing List Archive: MythTV: Commits

Ticket #11082: Deadlock when entering LiveTV

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noreply at mythtv

Sep 11, 2012, 3:01 PM

Post #1 of 2 (69 views)
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Ticket #11082: Deadlock when entering LiveTV

#11082: Deadlock when entering LiveTV
--------------------------------------------+-------------------------
Reporter: kenni | Owner:
Type: Bug Report - Hang/Deadlock | Status: new
Priority: minor | Milestone: unknown
Component: MythTV - General | Version: Master Head
Severity: medium | Keywords:
Ticket locked: 0 |
--------------------------------------------+-------------------------
I'm seeing this deadlock regularly after upgrading to pre0.26 from
0.25-fixes. This time I got a chance to attach gdb to the mythbackend
process and collect a backtrace before restarting it. Unfortunately I
didn't get the frontend backtrace as it didn't have any symbols installed.

Symptom: When I enter LiveTV on a frontend, the screen remains black with
no sound and no error messages of any kind.
Performing a tcpdump on the frontend reveals that no data are received
from the backend at this point. Looking at the backend reveals that the
backend happily records from my HDHR to a LiveTV file, but it doesn't
stream anything to the frontend.

I can exit back to the main menu with no issues and start LiveTV again
afterwards, again resulting in a black screen and the backend recording to
a new LiveTV file and not streaming anything to the frontend.

The backend log doesn't contain even a single line from the moment when I
trigger LiveTV on the frontend. The frontend does produce log-entries, but
no obvious errors are given (see attached file).

Restarting the backend fixes the issue.

I don't mind compiling a debug build or running with specific verbose
options if needed - just ping me.

Version: v0.26-rc2-2-ga625725

--
Ticket URL: <http://code.mythtv.org/trac/ticket/11082>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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noreply at mythtv

Sep 13, 2012, 1:20 PM

Post #2 of 2 (53 views)
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Re: Ticket #11082: Deadlock when entering LiveTV [In reply to]

#11082: Deadlock when entering LiveTV
----------------------------------------+-----------------------------
Reporter: kenni | Owner:
Type: Bug Report - Hang/Deadlock | Status: closed
Priority: minor | Milestone: unknown
Component: MythTV - General | Version: Master Head
Severity: medium | Resolution: Invalid
Keywords: | Ticket locked: 0
----------------------------------------+-----------------------------
Changes (by kenni):

* status: new => closed
* resolution: => Invalid

Comment:

The real issue causing the "deadlock" is that mythfrontend doesn't support
suspend-to-RAM. I already knew that and had a suspend/wakeup script to
restart the frontend. For other unrelated reasons, the restart script
stopped working and hence the frontend wasn't restarted on wakeup. I never
noticed as the frontend usually starts up before the TV is ready.

Restarting the backend reestablished the connection with the frontend, but
the real issue was the frontend being in an unconsistent state.

The lack of logs on the backend was apparently also unrelated and was
caused by a crashed mythlogserver:

{{{
mythlogserver[394]: segfault at 63 ip 0000000000000063 sp 00007f459904a678
error 14 in mythlogserver[400000+3000]
}}}

I'll enable core dumps and post a separate ticket if mythlogserver crashes
again.

Sorry about the noise.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/11082#comment:1>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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