From a867fed96f3a90c08aff70f0ca16dd84d0995e3f Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Tue, 27 Mar 2012 15:09:37 -0400 Subject: [PATCH] nohz: Fix stale jiffies update in tick_nohz_restart() commit 6f103929f8979d2638e58d7f7fda0beefcb8ee7e upstream. Fix tick_nohz_restart() to not use a stale ktime_t "now" value when calling tick_do_update_jiffies64(now). If we reach this point in the loop it means that we crossed a tick boundary since we grabbed the "now" timestamp, so at this point "now" refers to a time in the old jiffy, so using the old value for "now" is incorrect, and is likely to give us a stale jiffies value. In particular, the first time through the loop the tick_do_update_jiffies64(now) call is always a no-op, since the caller, tick_nohz_restart_sched_tick(), will have already called tick_do_update_jiffies64(now) with that "now" value. Note that tick_nohz_stop_sched_tick() already uses the correct approach: when we notice we cross a jiffy boundary, grab a new timestamp with ktime_get(), and *then* update jiffies. Signed-off-by: Neal Cardwell Cc: Ben Segall Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1332875377-23014-1-git-send-email-ncardwell@google.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- Reading git-format-patch failed