Ubuntu
linux package

  1. Bug #855199
  2. Comment #18

Comment 18 for bug 855199

Revision history for this message
Edward Donovan (edward.donovan) wrote : Re: 2.6.39 and later have lost "irqpoll" functionality

Ok, did a bunch more building and testing. They cant' be exhaustive, but these tests indicate that:

The config option that makes a difference is the sound driver for the PCI-E video card; the SND_HDA_INTEL option. So the conditions for IRQ trouble showing up are not only that a card is present in the PCI-E video slot, but also that the kernel engages the audio hardware on that card.

Under those conditions, a standard boot of every Linux version I've tried throws the "IRQ 19 - nobody cared" error during startup. (And on some cards, another error message for IRQ 18.) The USB hardware is trying to use IRQ 19 (in conflict with that sound hardware?), and USB performance suffers.

The 'irqpoll' boot option used to fix this problem, until that March 16 commit, "Merge branch 'irq-core-for-linus'". I've tested kernels from that snapshot through 3.1-pre, and if they contain that audio driver (which I'd like to continue to use), they give the IRQ errors even when irqpoll is active.

I'm not sure if I'm near the limits of my skills for troubleshooting this, but I'll try to 0