[mythtv] backend dying while mythweb is creating previews for recorded programs

Jim Westfall jwestfall at surrealistic.net
Tue Feb 22 17:40:15 UTC 2005


I also ran into this yesterday.  It segfaults everytime on my linuxppc 
backend.  I was able to narrow down where its happening, but havent had 
time to figure out why.

In the destructor of VideoOutputNull it calls Exit(), which calls 
VideoOutputNull::DeleteNullBuffers().

The segfault for me is occurring on the delete[] from this function.  It 
will usually occurs within the first 4 loops, but it isnt consistent.

void VideoOutputNull::DeleteNullBuffers()
{
    for (int i = 0; i < numbuffers + 1; i++)
    {
        delete [] vbuffers[i].buf;
        vbuffers[i].buf = NULL;
    }
}

I dont have a backtrace handy (at work) on the crashing thread, but in 
general is was a bunch of malloc_usable_size() followed by a kill().  The 
trace wouldnt got back past the malloc_usable_size(), gdb was claiming a 
corrupt stack.

jim

Risto Treksler <risto at elkhornbanff.ca> wrote [02.22.05]:
> Hi,
> 
> Has the code for static preview generation changed since .16
>  to make it happen in the background?
> 
> I see '(0 retries remaining)' in the logs for remote filetransfers
> How can I change that, so that it tries again?
> 
> 
> Here's what's happening:
> 
> i start by clearing out the png files
> #rm -f /mnt/store/*.png /var/www/html/mythweb/image_cache/*.png
> 
> then i go to the recorded_programs.php page in firefox and 
> when the backend is busy with commflagging or recording, 
> only a few preview images are shown
> 
> sometimes the backend seems to crash, 
> but upon further investigation it doesn't really segfault 
> but just exits gracefully right after a 
> 2005-02-22 00:00:16.986 Unknown file transfer socket: 18
> or similar, in the log
> 
> other times it gets stuck with tons of 
> "waiting for a thread" messages
> see preview-2.log
> i <ctrl-c>-ed the backend and got preview-4.bt
> 
> most of the time the files are actually created in /mnt/store
> but they just don't get copied over to image_cache
> so hitting reload copies them over
> 
> i have toyed with the idea of adding a timeout to let the file creation 
> complete before trying to copy the png over but no luck so far
> 
> i have added some debug statements to see what's going on
> preview-4.diff produces preview-4.html.txt
> and
> preview-7.diff produces preview-7.html.txt 
> (with the backend running inside a while loop)
> 
> i am stumped
> :(
> 
> -- 
> Risto Treksler
> Elkhorn Lodge
> Banff, Alberta, Canada
> -- 
> Risto Treksler
> Elkhorn Lodge
> Banff, Alberta, Canada










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