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Ticket #10541: SIGSEGV when EIT updating DB and channel change

 

 

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Apr 3, 2012, 10:32 AM

Post #1 of 13 (256 views)
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Ticket #10541: SIGSEGV when EIT updating DB and channel change

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------------+-------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - General | Status: new
Priority: major | Milestone: 0.25
Component: MythTV - DVB | Version: Master Head
Severity: high | Keywords:
Ticket locked: 0 |
--------------------------------------+-------------------------
I have a reproducible problem and tried several 0.25-pre versions since
the beginning of march. On a channel change for a recording and a running
(or maybe just ending) EIT update to the DB I get a SIGSEGV, almost every
second day. Sometimes empty files are created prior the crash of
mythbackend.

Reply from Michael:
Got a chance to look over the back trace and it's definitely a bug in our
code--the EIT scanner is not being shut down properly and is trying to
change channel on a null TVRec. It may be related to
http://code.mythtv.org/trac/ticket/10016 , but at this point it makes
sense to just create a new ticket for it. Please attach your log file and
back trace to the ticket (or let me know if it refuses to let you due to
the spam filter--which might not be working properly after the move to the
new server--and I can upload them for you).

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Apr 3, 2012, 10:57 AM

Post #2 of 13 (248 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: new
Priority: major | Milestone: 0.25
Component: MythTV - DVB | Version: Master Head
Severity: high | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------
Changes (by beirdo):

* type: Bug Report - General => Bug Report - Crash


Comment:

Please don't set the milestone, priority or severity.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:1>
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Apr 7, 2012, 9:23 AM

Post #3 of 13 (239 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: new
Priority: major | Milestone: 0.25
Component: MythTV - DVB | Version: Master Head
Severity: high | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

Comment (by danielk):

It looks line EITScanner::StopActiveScan() doesn't wait for the activeScan
to actually stop before setting rec to NULL. The attached patch should fix
it, but it isn't tested and I do want to write a nicer patch before
applying to master.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:2>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Apr 8, 2012, 4:43 AM

Post #4 of 13 (235 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: new
Priority: major | Milestone: 0.25
Component: MythTV - DVB | Version: Master Head
Severity: high | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

Comment (by angela.schmid@…):

Hi Daniel,
I pulled and activated the patch. A 0 byte file was created at 05:10,
however the logs show only ASK_RECORDING 30 seconds before. I think not
everything get logged, EIT debug messages overwrite the channel changing
messages. The frontend loosed connection and I had to ctrl-c the gdb'ed
backend. Attached is the dbg.txt and mythbackend.log.

Angela

2012-04-08 05:16:17.836800 E ThemeInfo: The theme
(myth://Temp [at] 127/remotethemes/trunk/Arclight) is missing a
themeinfo.xml file.
2012-04-08 05:16:27.829562 E MythSocket(28e6dc0:32): readStringList:
Error, timed out after 30000 ms.
2012-04-08 05:16:27.829600 C Protocol version check failure.
The response to MYTH_PROTO_VERSION was empty.
This happens when the backend is too busy to
respond,
or has deadlocked in due to bugs or hardware
failure.
2012-04-08 05:16:27.829607 E RemoteFile::openSocket(control socket):
Failed validation to server 127.0.0.1:6543
2012-04-08 06:16:17.834741 E ThemeInfo: The theme
(myth://Temp [at] 127/remotethemes/trunk/Arclight) is missing a
themeinfo.xml file.
2012-04-08 06:16:27.829810 E MythSocket(28a1710:32): readStringList:
Error, timed out after 30000 ms.
2012-04-08 06:16:27.829848 C Protocol version check failure.
The response to MYTH_PROTO_VERSION was empty.
This happens when the backend is too busy to
respond,
or has deadlocked in due to bugs or hardware
failure.
2012-04-08 06:16:27.829855 E RemoteFile::openSocket(control socket):
Failed validation to server 127.0.0.1:6543
2012-04-08 07:16:17.836478 E ThemeInfo: The theme
(myth://Temp [at] 127/remotethemes/trunk/Arclight) is missing a
themeinfo.xml file.
2012-04-08 07:16:27.832667 E MythSocket(2317e20:32): readStringList:
Error, timed out after 30000 ms.
2012-04-08 07:16:27.832703 C Protocol version check failure.
The response to MYTH_PROTO_VERSION was empty.
This happens when the backend is too busy to
respond,
or has deadlocked in due to bugs or hardware
failure.
2012-04-08 07:16:27.832710 E RemoteFile::openSocket(control socket):
Failed validation to server 127.0.0.1:6543

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:3>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Apr 8, 2012, 8:14 AM

Post #5 of 13 (232 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: new
Priority: major | Milestone: 0.25
Component: MythTV - DVB | Version: Master Head
Severity: high | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

Comment (by danielk):

Angela, please try this new patch.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:4>
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Apr 8, 2012, 1:31 PM

Post #6 of 13 (230 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+--------------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: infoneeded_new
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+--------------------------------
Changes (by danielk):

* priority: major => minor
* status: new => infoneeded_new
* severity: high => low
* milestone: 0.25 => 0.26


--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:5>
MythTV <http://code.mythtv.org/trac>
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Apr 12, 2012, 12:56 PM

Post #7 of 13 (226 views)
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Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+--------------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: infoneeded_new
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+--------------------------------

Comment (by angela.schmid@…):

In the last 4 days I had only one occasion, which was handled by the patch
successful. However, the recording started 1.5 minutes later, as you can
see from the log. Why does the recording earliest start, when the DB
writing is finished ?

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:6>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Apr 15, 2012, 9:50 AM

Post #8 of 13 (220 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+--------------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: infoneeded_new
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+--------------------------------

Comment (by angela.schmid@…):

Hello

No crashes anymore. However I see mythbackend hanging, which I have seen
in the past also without this patch.
I restarted mythbackend. EIT passive scanning started (17:39:26). A
recording was asked (17:39:39). EIT writing from 17:40:01 till 17:43:16.
During this time mythweb was not responding. Socket errors were
protocolied at 17:43:31. Recording was canceled 17:43:32. Mythweb did not
respond. A yet started mythfrontend had a log time to scan the recordings
in watch recordings. Had to restart mythbackend.

During "EITCache: Wrote 14 modified entries of 252 for channel 1002 to
database" messages, I think mythbackend comes unresponsive, this behaviour
has been seen before, also without this patch.
This time the recording has been canceled. In my previous comment, the
recording started 1.5 minutes later.

Run with " /usr/bin/mythbackend --syslog local7 --user mythtv -v
eit,general --loglevel debug". Attached mythbackend.zip and gdb1.txt (gdb
-p <pid>).
Why does mythbackend hang.

Angela

p.s. Why does MythTV not reuse prepared statements ? For each
insert/update/delete as far as I have seen, the SQL command is prepared on
each call. Why not preparing it once and reuse it. Sure needs some re-
preparing when the connection has to be re-astablished. Writing 2000 EIT
records needs 3 Minutes, which is in my eyes very long. This is on a Sandy
Bridge 2600K.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:7>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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Apr 18, 2012, 7:31 AM

Post #9 of 13 (219 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+--------------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: infoneeded_new
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution:
Keywords: | Ticket locked: 0
--------------------------------+--------------------------------

Comment (by angela.schmid@…):

Adding nobarrier to mount the ext4 FS where the MySQL DB is located fixed
the delay writing to the DB from up to 2 minutes to less than one second.

I had 8 events where the fix showed it works fine and doesn't crash
mythbackend anymore. Thanks Daniel.

When I had the long DB delays, it was still strange that recordings
started after finishing the EIT DB writing or even got cancelled. This
shouldn't be weighted to high, as I got the DB writing delay fixed.

Hope to see the patch in fixes/0.25.
Angela

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:8>
MythTV <http://code.mythtv.org/trac>
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May 4, 2012, 11:09 AM

Post #10 of 13 (203 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: closed
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution: fixed
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------
Changes (by Daniel Kristjansson <danielk@…>):

* status: infoneeded_new => closed
* resolution: => fixed


Comment:

In [changeset:a1d9015924480bb8a733452e294fb72ebbfce94a/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="a1d9015924480bb8a733452e294fb72ebbfce94a"
Fixes #10541. Fix EIT scanning deadlock.
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:9>
MythTV <http://code.mythtv.org/trac>
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May 4, 2012, 11:12 AM

Post #11 of 13 (204 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: closed
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution: fixed
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

Comment (by danielk):

The commit message should have said this fixes a crash. The deadlock
mentioned was introduced in an earlier version of the patch and removed in
a later version of the patch.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:10>
MythTV <http://code.mythtv.org/trac>
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May 27, 2012, 7:58 AM

Post #12 of 13 (194 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: closed
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution: fixed
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

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

In [changeset:6dce025ee1ac69e5a78c2e270b06aeff852765e7/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="6dce025ee1ac69e5a78c2e270b06aeff852765e7"
Fixes #10541. Fix EIT scanning deadlock.
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:11>
MythTV <http://code.mythtv.org/trac>
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May 29, 2012, 5:37 AM

Post #13 of 13 (192 views)
Permalink
Re: Ticket #10541: SIGSEGV when EIT updating DB and channel change [In reply to]

#10541: SIGSEGV when EIT updating DB and channel change
--------------------------------+-----------------------------
Reporter: angela.schmid@… | Owner: danielk
Type: Bug Report - Crash | Status: closed
Priority: minor | Milestone: 0.26
Component: MythTV - DVB | Version: Master Head
Severity: low | Resolution: fixed
Keywords: | Ticket locked: 0
--------------------------------+-----------------------------

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

In [changeset:a9edae22461ff7ef6749abaed21603fc8bf98cb7/mythtv]:
{{{
#!CommitTicketReference repository="mythtv"
revision="a9edae22461ff7ef6749abaed21603fc8bf98cb7"
Refs #10771. Revert "Fixes #10541. Fix EIT scanning deadlock."

This appears to be _causing_ a deadlock for warpme.

This reverts commit 6dce025ee1ac69e5a78c2e270b06aeff852765e7.
}}}

--
Ticket URL: <http://code.mythtv.org/trac/ticket/10541#comment:12>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
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