On 19/06/13 17:52, John Stultz wrote: > On 06/19/2013 08:25 AM, David Vrabel wrote: >> From: David Vrabel <david.vra...@citrix.com> >> >> The high resolution timer code gets notified of step changes to the >> system time with clock_was_set() or clock_was_set_delayed() calls. If >> other parts of the kernel require similar notification there is no >> clear place to hook into. >> >> Add a clock_was_set atomic notifier chain >> (clock_was_set_notifier_list) and call this in place of >> clock_was_set(). If the timekeeping locks are held, the calls are >> deferred to a new tasklet. >> >> The hrtimer code adds a notifier block to this chain and uses it to >> call (the now internal) clock_was_set(). Since the timekeeping code >> does not call the chain from the timer irq clock_was_set_delayed() and >> associated code can be removed. > > So on my initial quick review, this *looks* pretty reasonable. I get a > little worried about interface abuse (ie: random drivers trying to hook > into clock_was_set_notifier_list), but we can move that into > timekeeper_internal.h or something similar to limit that.
I can move the actual list to time.c but we still need to provide a register_clock_was_set_notifier() call in linux/time.h as the two current users (Xen and hrtimers) don't include and probably should not include timekeeper_internal.h. > The other issue here is we've been burned pretty badly in the past with > changes to clock_was_set(), as its key to keeping timers in line with > timekeeping. So this will need a fair amount of testing and run time > before this gets merged, so 3.12 is what we'd be targeting at the > earliest (its getting a bit late for taking changes for 3.11 anyway). hrtimer's clock_was_set() is called at the same point in the non-delayed case. For the delayed case, it used to be called at the beginning of the hrtimer softirq and now it is called from a tasklet, but if I understand this correctly, the tasklet softirq will be called before the hrtimer one so this should give the same behaviour. > If you want to try to push patch 1/4 in for 3.11 via the Xen tree, I'll > see about queuing the other three for hopefully 3.12. 3.12 is fine. I'd prefer to have a correct and well-tested fix merged. David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
