[SOLVED] Mythtv live-tv problem since kernel-3.4.4-3

[johnkdevnull]

I've had live tv crashing and freezing since upgrading to kernel-3.4.4-3 in Fedora 17 and now also kernel-3.4.4-5. I still have 3.4.3-1 installed thank goodness and can revert to that for trouble free TV viewing in Mythtv. I have an Hauppauge PVR150 that uses lirc_zilog module (to show an svideo stream from Sky box) and I have an Nvidia GeForce 9600 GT with kmod-nvidia module loaded. Neither of which gave me any issues in the previous kernel. It's the feed from the Hauppauge card that freezes. Recorded programs play back fine.

I can supply any info required but basically since it worked fine before and now doesn't, can anyone help pinpoint what changed between kernel 3.4.3-1 and 3.4.4-3 to cause this? I had a quick look at the kernel change log but since I'm no developer of any sort, I'm in the dark.

/var/log/messages below from when the video pauses.

Jul 8 21:19:29 oscar kernel: [ 286.351686] IRQ 16 might be stuck. Polling
Jul 8 21:19:38 oscar kernel: [ 295.342308] NVRM: Xid (0000:01:00): 16, Head 00000001 Count 00004a19
Jul 8 21:19:47 oscar kernel: [ 304.117202] IRQ 16 might be stuck. Polling
Jul 8 21:19:55 oscar kernel: [ 312.368113] NVRM: Xid (0000:01:00): 8, Channel 00000006
Jul 8 21:19:56 oscar mythbackend[1365]: 2012-07-08 21:19:56.750499 E DevRdB(/dev/video0): Poll giving up 2
Jul 8 21:19:56 oscar mythbackend[1365]: 2012-07-08 21:19:56.750548 E MPEGRec(/dev/video0): Device error detected
Jul 8 21:19:57 oscar kernel: [ 314.367123] NVRM: os_schedule: Attempted to yield the CPU while in atomic or interrupt context
Jul 8 21:19:59 oscar kernel: [ 316.367689] NVRM: Xid (0000:01:00): 16, Head 00000001 Count 00004da9
Jul 8 21:20:17 oscar kernel: [ 334.066216] IRQ 16 might be stuck. Polling

[johnkdevnull]

As usual, answering my own posts.. the issue was caused by the introduction of a kernel patch

unhandled-irqs-switch-to-polling.patch

which deals with 'faulty' PCI Bridge hardware (ASM1080). Apparently some cards behind this bridge end up with IRQs dropped which is bad. This patch was to try to recover/prevent that. However its unintended side effect was to decide prematurely in my case that I was having IRQ problems and thus introduced the glitches in playback by trying to recover from a non-existent problem. (I have my TV card and my NVidia card on that bridge)

Fixes include recompiling the kernel without the patch, or persuading the developer to increase his 'unhandled IRQ threshold' value from 9 to 12 or above. This increase lets my cards at least, work as normal.

I've emailed him with the info. We'll see if anything gets changed.