On Sun, Jan 29, 2012 at 9:44 AM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > So it may be completely and utterly broken for some subtle reason, but > I don't see what it would be. It seems to clean up and simplify the > logic, and remove all the bogus workarounds for the fact that we used > to do things stupidly. > > But maybe there's some reason for those "stupid" things. I just don't see it. Hmm. Ok, so I see one reason for it. The silly extraneous "set task to TASK_UNINTERRUPTIBLE" shouldn't matter normally - even if there are spurious wakeups (say, disk IO while taking a page fault - not that I see why we'd be on any wait queues yet), we'll just schedule a bit more than we need in the extremely unlikely case that they hit us. But for RT tasks with higher priorities, looping - even if we call schedule() all the time - can cause livelocks. Damn. So while I don't think the spurious wakeup is a big issue (I don't think it happens in practice), it could lead to problems. I think we could possibly use the "flags" field to do that "are we just about to get woken up" logic, and set TASK_UNINTERRUPTIBLE in the loop - and just clear "flags" before doing the wakeup (the same way we used to clear "task"). Dunno. Ideas? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html