[PATCH 1/3] hrtimer: make the futex() system call use the perprocess slack value

From: Arjan van de Ven
Date: Wed Sep 10 2008 - 23:30:59 EST

From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Subject: [PATCH] hrtimer: make the futex() system call use the per process slack value

This patch makes the futex() 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 <arjan@xxxxxxxxxxxxxxx>
kernel/futex.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 4cd5b43..8af1002 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1296,10 +1296,14 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
if (!abs_time)
else {
+ unsigned long slack;
+ slack = current->timer_slack_ns;
+ if (rt_task(current))
+ slack = 0;
hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
hrtimer_init_sleeper(&t, current);
- hrtimer_set_expires(&t.timer, *abs_time);
+ hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);

hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&t.timer))

Arjan van de Ven Intel Open Source Technology Centre
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