Re: PREEMPT_RT vs i915

Sebastian Andrzej Siewior
2025-07-10T06:30:16Z

On 2025-07-09 15:04:27 [-0700], Matthew Brost wrote:
> > And IIRC the other remaining problem with RT was the spinlocks used
> > inside tracepoints (which is uncore lock, and probably some vblank
> > locks). So that too needs some kind of solution because it's going to
> > very hard to debug the timing sensitive parts without the tracepoints.
>
> A bit of a drive-by comment, but taking locks inside tracepoints seems
> like a pretty horrible idea in general. We've managed to write an entire
> driver (Xe) from scratch and bring it up without doing this. I'd be very
> surprised if this is truly necessary in i915.

Steven made suggestions how to get around it make it work but my
impression was that this was not appreciated by the i915 side.
The general unwritten rule is to not to take any locks but simply assign
variables.

> Matt

Sebastian