[tip:sched/core] sched: Fix hrtick_start() on UP

[tip-bot for Wanpeng Li <tipbot@zytor.com>]

Commit-ID:  868933359a3bdda25b562e9d41bce7071edc1b08
Gitweb:     http://git.kernel.org/tip/868933359a3bdda25b562e9d41bce7071edc1b08
Author:     Wanpeng Li <wanpeng.li@linux.intel.com>
AuthorDate: Wed, 26 Nov 2014 08:44:06 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 4 Feb 2015 07:52:28 +0100

sched: Fix hrtick_start() on UP

The commit 177ef2a6315e ("sched/deadline: Fix a precision problem in
the microseconds range") forgot to change the UP version of
hrtick_start(), do so now.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Fixes: 177ef2a6315e ("sched/deadline: Fix a precision problem in the microseconds range")
[ Fixed the changelog. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1416962647-76792-7-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d59652d..5091fd4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -492,6 +492,11 @@ static __init void init_hrtick(void)
  */
 void hrtick_start(struct rq *rq, u64 delay)
 {
+	/*
+	 * Don't schedule slices shorter than 10000ns, that just
+	 * doesn't make sense. Rely on vruntime for fairness.
+	 */
+	delay = max_t(u64, delay, 10000LL);
 	__hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,
 			HRTIMER_MODE_REL_PINNED, 0);
 }