releases/3.19.2/sched-fix-hrtick_start-on-up.patch

   1 From 868933359a3bdda25b562e9d41bce7071edc1b08 Mon Sep 17 00:00:00 2001
   2 From: Wanpeng Li <wanpeng.li@linux.intel.com>
   3 Date: Wed, 26 Nov 2014 08:44:06 +0800
   4 Subject: sched: Fix hrtick_start() on UP
   5
   6 From: Wanpeng Li <wanpeng.li@linux.intel.com>
   7
   8 commit 868933359a3bdda25b562e9d41bce7071edc1b08 upstream.
   9
  10 The commit 177ef2a6315e ("sched/deadline: Fix a precision problem in
  11 the microseconds range") forgot to change the UP version of
  12 hrtick_start(), do so now.
  13
  14 Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
  15 Fixes: 177ef2a6315e ("sched/deadline: Fix a precision problem in the microseconds range")
  16 [ Fixed the changelog. ]
  17 Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
  18 Cc: Juri Lelli <juri.lelli@arm.com>
  19 Cc: Kirill Tkhai <ktkhai@parallels.com>
  20 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  21 Link: http://lkml.kernel.org/r/1416962647-76792-7-git-send-email-wanpeng.li@linux.intel.com
  22 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24
  25 ---
  26  kernel/sched/core.c |    5 +++++
  27  1 file changed, 5 insertions(+)
  28
  29 --- a/kernel/sched/core.c
  30 +++ b/kernel/sched/core.c
  31 @@ -490,6 +490,11 @@ static __init void init_hrtick(void)
  32   */
  33  void hrtick_start(struct rq *rq, u64 delay)
  34  {
  35 +       /*
  36 +        * Don't schedule slices shorter than 10000ns, that just
  37 +        * doesn't make sense. Rely on vruntime for fairness.
  38 +        */
  39 +       delay = max_t(u64, delay, 10000LL);
  40         __hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
  41                         HRTIMER_MODE_REL_PINNED, 0);
  42  }