[mythtv-users] Segfault while tuning channel in mythtv 31.0

[Charles Bovy]

> On 17 Jul 2020, at 17:37, David Hampton <mythtv at love2code.net> wrote:
> 
> On Fri, 2020-07-17 at 14:26 +0200, Thomas Börkel wrote:
>> Hi all,
>> 
>> I just upgraded from mythtv 30.0 to 31.0 (fixes) on Gentoo and now I
>> get
>> a segfault when it is tuning a channel.
>> 
>> Happens when EIT scan starts or when I start Live TV. Did not test
>> recording yet.
>> 
>> Output in gdb for Live TV:
>> 
>> Thread 8 "TVRecEvent" received signal SIGSEGV, Segmentation fault.
>> [Switching to Thread 0x7fe57b7fe700 (LWP 30677)]
>> 0x00007fe5a4651a6c in ?? () from /usr/lib64/libmythtv-31.so.31
>> 
>> Attaching full gdb.txt.
>> 
>> After upgrading, I went into mythtv-setup and noticed that the
>> "DVBInput" is configured as capture cards delivery system, which is
>> not
>> an option in the select box. So, I changed that to "DVB-S2". But that
>> did not change anything regarding the crash.
>> 
>> Any hints would be greatly appreciated.
> 
> I'm assuming that everything before line 480 is old cruft as it
> reference a Qt4 library.  Qt4 hasn't been supported since 0.27.  If
> those aren't old stack traces, start there. Current MythTV requires
> Qt5.
> 
> The last stack frame in the file crashed here:
> 
> Thread 8 (Thread 0x7fe57b7fe700 (LWP 30677)):
> #0  0x00007fe5a4651a6c in  () at /usr/lib64/libmythtv-31.so.31
> #1  0x00007fe5a46523cf in  () at /usr/lib64/libmythtv-31.so.31
> #2  0x00007fe5a465c036 in  () at /usr/lib64/libmythtv-31.so.31
> #3  0x00007fe5a448966d in  () at /usr/lib64/libmythtv-31.so.31
> #4  0x00007fe5a4531371 in TVRec::SetupSignalMonitor(bool, bool, bool)
> () at /usr/lib64/libmythtv-31.so.31
> #5  0x00007fe5a45384f0 in TVRec::TuningFrequency(TuningRequest const&)
> () at /usr/lib64/libmythtv-31.so.31
> #6  0x00007fe5a453d63c in TVRec::HandleTuning() () at
> /usr/lib64/libmythtv-31.so.31
> #7  0x00007fe5a453da67 in TVRec::run() () at /usr/lib64/libmythtv-
> 31.so.31
> #8  0x00007fe5a3afc887 in MThread::run() () at /usr/lib64/libmythbase-
> 31.so.31
> #9  0x00007fe5a27aaf4c in  () at /usr/lib64/libQt5Core.so.5
> #10 0x00007fe5a36c9f27 in start_thread () at /lib64/libpthread.so.0
> #11 0x00007fe5a2393b7f in clone () at /lib64/libc.so.6
> 
> This looks wrong as gdb should have names for all the functions in
> libmythtv-31. Is this a stripped image? Can you build an image with
> debug symbols still present? That would be extremely helpful.


Hi Thomas,

Are you using a physical DVB adapter or a virtual one (like dvbloopback)? I’m experiencing similar issue where the issue is not in MythTV but in the virtual adapter. It has to do with the DVBv5 calls (FE_GET_PROPERTY) in v31. Commenting them (in dvbchannel.cpp) will get you back to a working version as a workaround. 

Regards,

Charles