On Thu, Jul 10, 2025 at 08:41:36AM +0200, Sebastian Andrzej Siewior wrote: > On 2025-07-09 23:09:22 [+0300], Ville Syrjälä wrote: > > On Wed, Jul 09, 2025 at 09:44:43PM +0200, Sebastian Andrzej Siewior wrote: > > > On 2025-07-09 20:30:26 [+0300], Ville Syrjälä wrote: > > > > > > > > > > It seems like the critical uncore lock is currently held in a lot of > > > > > places and potentially for a long time. > > > > > > > > It shouldn't be held for that long. I think it should just be > > > > a raw spinlock. > > > > > > What about I resubmit the series and we look again? I don't think the > > > lock should be made raw just to be done with it. > > > > Until someone actually does the work to confirm the thing is working > > reliably there's no point in posting anything. > > Well it works on my machine and this machine dose not pass the code > paths that I patch. > > Every patch made was done because someone reported an error/ warning and > confirmed afterwards that the patch fixes it for them and they can use > the machine and don't observe anything. > > > 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. > > no, not just that. Making the lock raw led to latency spikes in simple > spikes and I just disabled trace points. It could be worked around by > taking the lock if the tracepoint is enabled and then invoking the > tracepoint unconditionally and not taking the lock anymore. Steven made > a suggestion a while ago how to put this in macro as far as I remember.
When this was last discussed I suggested that there should be a versions of the tracepoint macros that do the sampling outside the lock, but that wasn't deemed acceptable for whatever reason. I don't even know why the current macros are doing the sampling while holding the lock... -- Ville Syrjälä Intel
