[Icecast-dev] Segmentation fault issue with new install

Jan-Pieter Veen Jan-Pieter at veenweb.nl
Thu Apr 30 08:03:35 PDT 2015 

2015-04-29 8:57 GMT+02:00 "Thomas B. Rücker" <thomas at ruecker.fi>:

> On 04/28/2015 02:27 PM, Jan-Pieter wrote:
> > Hi all,
> > see my reply inline.
> > Cheers, Jan-Pieter
> >
> >
> > 2015-04-26 7:23 GMT+02:00 "Thomas B. Rücker" <thomas at ruecker.fi
> > <mailto:thomas at ruecker.fi>>:
> >
> >     On 04/25/2015 07:32 PM, Jan-Pieter wrote:
> >     > Hi all,
> >     >
> >     > I am a long-time user of Icecast, always without problems. However
> i
> >     > made a new setup using icecast 2.4.1 on a fresh and quick CentOS
> >     VPS.
> >
> >     EPEL package or from somewhere else?
> >
> > it's just a standard CentOS 6.6 release, no EPEL. Distri from hosting
> > provider. [root at h2429770 tmp]# uname -a
> > Linux h2429770.stratoserver.net <http://h2429770.stratoserver.net>
> > 2.6.32-042stab103.6 #1 SMP Wed Jan 21 13:07:39 MSK 2015 x86_64 x86_64
> > x86_64 GNU/Linux
> >
> >
> >
> >     > The issue is that starting icecast gives a segmentation fault at
> >     > around 80% of all starts. No core file nor a entry in error.log
> >     is posted.
> >
> >     Enable core dumps using "ulimit -c unlimited". The PWD from where you
> >     start Icecast needs to be writeable.
> >
> >
> > Even with ulimit -c unlimited and running from a writable PWD no core
> > is dumped.
>
> Seems it's a bit more involved on Centos6:
> http://www.unixmen.com/how-to-enable-core-dumps-in-rhel6/
> I've tried it successfully on a quick install of centos6 that I've
> compiled 2.4.2 on and am going to try with your config.
> (As you don't use url-auth for sources, 2.4.1 is safe for you)
>
> I followed this steps, but still no core file with this type of segfault.
Other programs which segfaults do produce a core dump however. so bit
strange...


>
> >     > In the remaining 20% of the starts icecast start with no problem.
> >     >
> >     > Contents of the error.log with a succesfull start (20% of
> >     icecast starts):
> >     > [2015-04-25  21:08:40] INFO main/main Icecast 2.4.1 server started
> >     > [2015-04-25  21:08:40] INFO connection/get_ssl_certificate No SSL
> >     > capability
> >     > [2015-04-25  21:08:40] INFO stats/_stats_thread stats thread
> started
> >     > [2015-04-25  21:08:40] INFO yp/yp_update_thread YP update thread
> >     started
> >     > [2015-04-25  21:08:40] INFO source/source_fallback_file mountpoint
> >     > /geen-uitzending.mp3 is reserved
> >     > [2015-04-25  21:08:40] WARN format/format_get_type Unsupported or
> >     > legacy stream type: "audio/mpeg". Falling back to generic minimal
> >     > handler for best effort.
> >     > [2015-04-25  21:08:40] WARN source/source_fallback_file mountpoint
> >     > "/geen-uitzending.mp3" already reserved
> >     > [2015-04-25  21:08:40] INFO source/source_main listener count on
> >     > /geen-uitzending.mp3 now 0
> >     >
> >     >
> >     > Contents of error.log with a segmentation fault direct after start
> >     > (80% of icecast starts):
> >     > 2015-04-25  21:09:05] INFO main/main Icecast 2.4.1 server started
> >     > [2015-04-25  21:09:05] INFO connection/get_ssl_certificate No SSL
> >     > capability
> >     > [2015-04-25  21:09:05] INFO yp/yp_update_thread YP update thread
> >     started
> >     > [2015-04-25  21:09:05] INFO source/source_fallback_file mountpoint
> >     > /geen-uitzending.mp3 is reserved
> >     > [2015-04-25  21:09:05] WARN format/format_get_type Unsupported or
> >     > legacy stream type: "audio/mpeg". Falling back to generic minimal
> >     > handler for best effort.
> >     > [2015-04-25  21:09:05] INFO stats/_stats_thread stats thread
> started
> >
> >     Can you attach your icecast.xml please (with passwords removed)?
> >     This might help reproduce the problem.
> >
> >
> > I attached icecast.xml. I also turned debug errorlog level on.
> > Results with debug on:
> >
> > good start:
> > [2015-04-28  15:56:39] INFO main/main Icecast 2.4.1 server started
> > [2015-04-28  15:56:39] DBUG yp/yp_recheck_config Updating YP
> configuration
> > [2015-04-28  15:56:39] INFO connection/get_ssl_certificate No SSL
> > capability
> > [2015-04-28  15:56:39] INFO stats/_stats_thread stats thread started
> > [2015-04-28  15:56:39] INFO yp/yp_update_thread YP update thread started
> > [2015-04-28  15:56:39] INFO source/source_fallback_file mountpoint
> > /geen-uitzending.mp3 is reserved
> > [2015-04-28  15:56:39] DBUG connection/connection_complete_source
> > sources count is 0
> > [2015-04-28  15:56:39] WARN format/format_get_type Unsupported or
> > legacy stream type: "audio/mpeg". Falling back to generic minimal
> > handler for best effort.
> > [2015-04-28  15:56:39] DBUG connection/connection_complete_source
> > source is ready to start
> > [2015-04-28  15:56:39] DBUG source/source_init Source creation complete
> > [2015-04-28  15:56:39] WARN source/source_fallback_file mountpoint
> > "/geen-uitzending.mp3" already reserved
> > [2015-04-28  15:56:39] INFO source/source_main listener count on
> > /geen-uitzending.mp3 now 0
> > [2015-04-28  15:56:39] DBUG stats/modify_node_event update global
> > sources (1)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new source stat
> > /geen-uitzending.mp3
> > [2015-04-28  15:56:39] DBUG stats/modify_node_event update global
> > source_client_connections (1)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > listeners (0)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > listenurl (http://stream3.server7.nl:80/geen-uitzending.mp3)
> > [2015-04-28  15:56:39] DBUG stats/modify_node_event update global
> > source_total_connections (1)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > slow_listeners (0)
> > [2015-04-28  15:56:39] DBUG stats/modify_node_event update
> > "/geen-uitzending.mp3" listeners (0)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > listener_peak (0)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > stream_start (Tue, 28 Apr 2015 15:56:39 +0200)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > stream_start_iso8601 (2015-04-28T15:56:39+0200)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > total_bytes_read (0)
> > [2015-04-28  15:56:39] DBUG stats/process_source_event new node
> > total_bytes_sent (0)
> > [2015-04-28  15:56:39] DBUG stats/modify_node_event update
> > "/geen-uitzending.mp3" listeners (0)
> > [2015-04-28  15:56:40] DBUG slave/_slave_thread checking master stream
> > list
>
> I currently suspect it's something interacting with the stats thread and
> the two identical fallbacks.
>
> Agree, seems to have something to do with stats thread. But I tested also
with dual fall back files. Same issue. See attached new configfile.

>
> >
> > bad start (segfault):
> > [2015-04-28  15:56:53] INFO main/main Icecast 2.4.1 server started
> > [2015-04-28  15:56:53] DBUG yp/yp_recheck_config Updating YP
> configuration
> > [2015-04-28  15:56:53] INFO connection/get_ssl_certificate No SSL
> > capability
> > [2015-04-28  15:56:53] INFO yp/yp_update_thread YP update thread started
> > [2015-04-28  15:56:53] INFO source/source_fallback_file mountpoint
> > /geen-uitzending.mp3 is reserved
> > [2015-04-28  15:56:53] DBUG connection/connection_complete_source
> > sources count is 0
> > [2015-04-28  15:56:53] WARN format/format_get_type Unsupported or
> > legacy stream type: "audio/mpeg". Falling back to generic minimal
> > handler for best effort.
> > [2015-04-28  15:56:53] DBUG connection/connection_complete_source
> > source is ready to start
> > [2015-04-28  15:56:53] DBUG source/source_init Source creation complete
> > [2015-04-28  15:56:53] INFO stats/_stats_thread stats thread started
> > [2015-04-28  15:56:53] DBUG stats/process_source_event new source stat
> > /geen-uitzending.mp3
> >
> >
> >
> >
> >
> >
> >     > Both the stream and the fallback file are .mp3 type. I tried
> >     removing
> >     > the fallback entry. Then icecast starts always normally. So it
> seems
> >     > related to the .mp3 fallback.
> >     >
> >     > Also I tried to launch icecast with strace, and this NEVER fails.
> No
> >     > segmentation faults!
> >     >
> >     >
> >     > Any idea what's going wrong? Something going wrong with timing on a
> >     > fast server?
> >
> >     It sounds like you've found a race condition. I'm not exactly sure
> >     what's happening though.
> >     By the log output something seems to be instantly accessing the
> >     stream.
> >     Notice the order of the stats_thread is different in both.
> >
> >
> > Yes this is the only interesting thing. The segfault only happens when
> > "INFO stats/_stats_thread stats thread started"
> > is missing in the error.log. So with every succesful start this line
> > gets logged, and if the line is missing the segfault occurs.
>
> I suspect it's a very close race that might only occur on that specific
> configuration/virtualization.
> In such case invasive things like strace and valgrind won't help us. A
> coredump might reveal something, but isn't guaranteed.
>
> What BTW confuses me is that you override the mountpoint configuration
> to ogg/vorbis, but fall back to an mp3 file.
>
> Sorry my mistake. Tried changing things here, but did not change the
behaviour. In the attached config file I set it all to mp3 and problem
persists.
Agree that it has probably something to do with virtualization platform. My
VPS is running  in a Virtuozzo container. However with other programs no
issue at all. Looks to me still as a timing issue that somehow the stats
thread is not started causing the segfault when loading the fallback
stream. Maybe a small noop/sleep just before the statsthread will solve my
issue...


> > I also tried running using valgrind on advice of Philipp, but when
> > running with valgrind the segfault does not occur and icecast starts
> > normally... (same as with gdb)
>
> yeah, expected.
>
> I tried your config on a centos 6 machine and couldn't reproduce it. How
> many CPU cores / threads does it have?
>
> 4 cores/threads.



>
> Cheers
>
> Thomas
>
> Thanks!
Jan-Pieter

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