From a9cf55b2861057a213e610da2fec52125439a11d Mon Sep 17 00:00:00 2001 From: Paul Turner Date: Thu, 21 Jul 2011 09:43:32 -0700 Subject: [PATCH] sched: Expire invalid runtime Since quota is managed using a global state but consumed on a per-cpu basis we need to ensure that our per-cpu state is appropriately synchronized. Most importantly, runtime that is state (from a previous period) should not be locally consumable. We take advantage of existing sched_clock synchronization about the jiffy to efficiently detect whether we have (globally) crossed a quota boundary above. One catch is that the direction of spread on sched_clock is undefined, specifically, we don't know whether our local clock is behind or ahead of the one responsible for the current expiration time. Fortunately we can differentiate these by considering whether the global deadline has advanced. If it has not, then we assume our clock to be "fast" and advance our local expiration; otherwise, we know the deadline has truly passed and we expire our local runtime. Signed-off-by: Paul Turner Reviewed-by: Hidetoshi Seto Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20110721184757.379275352@google.com Signed-off-by: Ingo Molnar --- Reading git-format-patch failed