Nicolas Pitre <nico@xxxxxxx> wrote: > > I mean, the darned thing is called from sched_clock(), which can be > > concurrently called on separate CPUs and which can be called from > > interrupt context (with an arbitrary nesting level!) while it was running > > in process context. > > Yes! And this is so on *purpose*. Please take some time to read the > comment that goes along with it, and if you're still not convinced then > look for those explanation emails I've already posted. I agree with Nicolas on this. It's abominably clever, but I think he's right. The one place I remain unconvinced is over the issue of preemption of a process that is in the middle of cnt32_to_63(), where if the preempted process is asleep for long enough, I think it can wind time backwards when it resumes, but that's not a problem for the one place I want to use it (sched_clock()) because that is (almost) always called with preemption disabled in one way or another. The one place it isn't is a debugging case that I'm not too worried about. > > /* > > * Caller must provide locking to protect *caller_state > > */ > > NO! This is meant to be LOCK FREE! Absolutely. David -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
