[mythtv-commits] Ticket #1887: invalid PAT in recordings causes Frontend Crash, Backtrace Attached...

[MythTV]

#1887: invalid PAT in recordings causes Frontend Crash, Backtrace Attached...
--------------------+-------------------------------------------------------
 Reporter:  jochen  |        Owner:  danielk
     Type:  defect  |       Status:  new    
 Priority:  minor   |    Milestone:  0.20   
Component:  mythtv  |      Version:  head   
 Severity:  medium  |   Resolution:         
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Changes (by Janne <janne-mythtv at grunau.be>):

  * summary:  Frontend Crash, Backtrace Attached... => invalid PAT in
              recordings causes Frontend Crash, Backtrace
              Attached...

Comment:

 psofa from irc got a stream that crashes mythfrontend or mythtv
 reproducably. The backtraces look very similar to the attached.
 The problem in this stream [http://www.grunau.be/invalid_pat.ts] is an
 invalid PAT.

 Following block is from the mythtv output with DEBUG_SI in mpegts.c.
 The first 3 PAT look like this one:
 {{{
 PAT:
 00000000  00 b0 0d 00 01 c7 00 00 00 01 e4 09 fa 3f 23 d6 .............?#.
 sid=0x1 sec_num=0/0
 MPEG Program Number=0x1 pid=0x409 req_sid=0x1
 Found program number!
 }}}

 But the next contains 0x00 as program number:
 {{{
 PAT:
 00000000  00 b0 0d 00 01 c9 00 00 00 01 e0 00 49 d9 e4 47 ............I..G
 sid=0x1 sec_num=0/0
 MPEG Program Number=0x1 pid=0x0 req_sid=0x1
 New PAT!
 new_service: sid=0x0001 provider='' name='MPEG Program 1'
 Found program number!
 Closing Filter: pid=0x409
 Closing PMT Filter: pid=0x409
 Opening Filter: pid=0x0
 Filter Already Exists
 Closing Filter: pid=0x0
 Closing PAT Filter: pid=0x0
 zsh: segmentation fault  mythtv -v all /pub/1747_20060601015601.mpg
 }}}

 this recreates the original PAT filter and the segfault is caused by a
 dangling pointer to the old one.

 It seems that there is a race condition in the writing PAT code.

 psofa sees this error while channel zapping with his DVB-S card but not
 with DVB-T.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/1887>
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