the following patches are from the PREEMPT_RT queue. It is mostly about disabling interrupts/preemption which leads to problems. Patches 1-4 are independent of PREEMPT_RT.
Unfortunately DRM_I915_LOW_LEVEL_TRACEPOINTS had to be disabled because it acquires locks from within trace points. It has been pointed out in the previous post that this makes any kind of debugging impossible. Making the uncore.lock a raw_spinlock_t doubles the latencies in my limited testing [0]. I don't know the difference on other hardware. Also it worries me a little that wait_for_atomic() has 50ms as the upper spin/wait limit if the condition does not become true.
I tested it on a SandyBridge with built-in i915 by using X, OpenGL and playing videos without noticing any warnings. However, some code paths were not entered.
[0] https://lore.kernel.org/all/20211006164628.s2mtsdd2jdbfyf7g@linutronix.de/
Sebastian