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Subject[PATCH 2/3] hrtimer: make the nanosleep() syscall use the per process slack

From: Arjan van de Ven <>
Subject: [PATCH] hrtimer: make the nanosleep() syscall use the per process slack

This patch makes the nanosleep() system call use the per process
slack value; with this users are able to externally control existing
applications to reduce the wakeup rate.

Signed-off-by: Arjan van de Ven <>
kernel/hrtimer.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index a022209..9a4c901 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1563,9 +1563,14 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
struct restart_block *restart;
struct hrtimer_sleeper t;
int ret = 0;
+ unsigned long slack;
+ slack = current->timer_slack_ns;
+ if (rt_task(current))
+ slack = 0;

hrtimer_init_on_stack(&t.timer, clockid, mode);
- hrtimer_set_expires(&t.timer, timespec_to_ktime(*rqtp));
+ hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
if (do_nanosleep(&t, mode))
goto out;


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