> I mean, I understand that the GUI thread in question might be heavily pre-empted by medium-priority threads, but eventually the GUI thread is going to be give

> I mean, I understand that the GUI thread in question might be heavily pre-empted by medium-priority threads, but eventually the GUI thread is going to be given enough time to finish whatever it was doing with my lock, and life will go on. Is this behavior somehow unexpected or counterintuitive? The mistake people make is, they think "my high-priority thread has to be active every 10ms, and the low-priority thread doesn't do much work with the lock held, 1ms max, so I'm totally fine, there's 9ms of safety factor there". Priority inversion is why that logic is wrong.