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Sporadic full system hang on playback under 8.4.1
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Author:  Liv2Cod [ Sat Jun 11, 2016 4:38 am ]
Post subject:  Sporadic full system hang on playback under 8.4.1

My buddy and I have four myth boxes between us, two FE/BE machines and two FE only. All are built on one of the relatively new quadcore Celeron parts with built in Intel graphics, the Q1900 if memory serves me. With help from brfransen and others, we've gotten VAAPI working (at least on some machines), but we've never shaken off this complete system hang problem.

It happens when the system is playing back recorded HDTV on the internal player. It happens whether using accelerated graphics or not. We'll be playing a show and suddenly the screen will either freeze, or will freeze with a short loop of sound (about 1/4 second looping continuously). At this point, there is nothing we can do besides power off the box! You can't SSH into it, you can't get its attention with the remote or keyboard -- nothing at all will break it out of the loop or freeze state. You can't even get another TTY session up using the function keys. It's dead, Jim, and it can't come back.

I've looked and looked for any logs or evidence of what the problem might be. I cannot find any evidence in the logs I've searched. I believe it to be related to the graphics system, but that's just based on intuition more than any evidence. I wish I could pin it on the Intel driver under VAAPI but I've discovered that, even though VAAPI is installed on all four machines, the acceleration is only working on two of them. The other two have VAAPI installed, and show it with "vainfo", but fall back to ffmpeg during playback. Mind you, all four have identical hardware and are running the same revision of LinHES.

I'm going to visit my buddy this weekend and I plan to do a full reinstall of LinHES using the latest ISO recently dropped. My feeling is that perhaps some files were left in an unclean state from our previous machinations and a clear start will help. Of course, we can't do that with the database as my friend has thousands of shows in his backend and doesn't want to lose them. So we'll save and restore the database, at least for the backend.

I'm just curious if anyone else has seen the hard lock-up in another context, or if it only happens with the Intel driver. And, of course, if anyone has an idea of how to find out what's wrong when it actually freezes.


P.S. This problem is not specific to 8.4.1. We first saw it with 8.4, then it got better with some of the files added. When we upgraded to 8.4.1 the problem got worse. That's why we're hoping a clean install helps it now.

Author:  brfransen [ Sat Jun 11, 2016 8:28 am ]
Post subject:  Re: Sporadic full system hang on playback under 8.4.1

I saw the looping sound freeze years ago and I think it ended up being a hard drive that was slowly going bad. It could have been a could have been something else as there were some other updates that I did at the same time. All of my LinHES boxes have nvidia graphics and have been very stable for quite a few years.

There are only 12 commits between R8.4 and R8.4.1 and over half of those are nvidia related. Since you don't have nvidia those pkgs shouldn't even be installed. The rest are small changes but nothing that jumps out at me as possibly making a difference related to this.

What are the files that you have had to add/change/modify to get VAAPI working? Are the changes something we could add to when the intel driver is selected?

Running mythfrontend -v playback might give some more insight but since the lockup is happening at the system level maybe not.

I just built and pushed to testing a newer version of the intel driver if you want to give that a try.

Author:  Liv2Cod [ Sat Jun 11, 2016 4:48 pm ]
Post subject:  Re: Sporadic full system hang on playback under 8.4.1

Maybe we started with 8.3. I remember you did some Intel driver stuff for me and later pushed it into the main repo. The thing that prevents any diagnostics is this total hang -- I strongly suspect when it hangs it can't even write to the log file. Even when you give it a power switch interrupt (short push on power switch) it does not shutdown properly like its supposed to. It's a really HARD hang.

Since this has happened with numerous hard disks and even using networked hard disks, I'm pretty sure its not associated with a failing hard disk. We have a great diversity of everything except motherboards -- they are all using the same m/b (which includes the Celeron processor). It could be a motherboard BIOS issue, which may explain why we're not seeing more of it.

For a long time I suspected some kind of interrupt contention between networking and the hard disk. Few things, in my experience, can lock up a computer quicker and harder than a networking problem. Since it always happens during playback on the internal player, some kind of video issue is logical. But this happens using ffmpeg as well, not just vaapi. I don't know which parts of the Intel driver are used in "normal" ffmpeg vs vaapi.

We'll keep shotgunning it until we come up with something... Thanks for the updated driver in the testing repo.

-- Joe

Author:  Liv2Cod [ Sun Jun 12, 2016 12:39 pm ]
Post subject:  Re: Sporadic full system hang on playback under 8.4.1

Some success!

Installing the 8.4.1 iso went very well -- good job on the iso itself. The one install glitch is that I had to use "force vesa" during installation to get it to work. For some reason, the newer Intel graphics part causes a lot of mischief during the install process. The graphics are offset by about 40% of the screen width during install, but they wrap around so you can see the options you're checking. This is a vesa-only problem.

After installation I ran as root from a shell and it easily identified and installed the Intel graphics support. I restarted (just for good measure) and chose the VAAPI Normal profile and all three LinHES boxes now use the accelerated graphics. Yea!

The only unknown at this point is the sporadic freeze-ups. It will take a week or so to reveal if that's going to be an ongoing problem. Call me "cautiously optimistic" at this point...

-- Joe

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