From c19384b5b296905d4988c7c684ff540a0f9d65be Mon Sep 17 00:00:00 2001
From: Pierre Peiffer <pierre.peiffer@bull.net>
Date: Wed, 9 May 2007 02:35:02 -0700
Subject: Make futex_wait() use an hrtimer for timeout
This patch modifies futex_wait() to use an hrtimer + schedule() in place of
schedule_timeout().
schedule_timeout() is tick based, therefore the timeout granularity is the
tick (1 ms, 4 ms or 10 ms depending on HZ). By using a high resolution timer
for timeout wakeup, we can attain a much finer timeout granularity (in the
microsecond range). This parallels what is already done for futex_lock_pi().
The timeout passed to the syscall is no longer converted to jiffies and is
therefore passed to do_futex() and futex_wait() as an absolute ktime_t
therefore keeping nanosecond resolution.
Also this removes the need to pass the nanoseconds timeout part to
futex_lock_pi() in val2.
In futex_wait(), if there is no timeout then a regular schedule() is
performed. Otherwise, an hrtimer is fired before schedule() is called.
[akpm@linux-foundation.org: fix `make headers_check']
Signed-off-by: Sebastien Dugue <sebastien.dugue@bull.net>
Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/futex.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
(limited to 'include/linux/futex.h')
diff --git a/include/linux/futex.h b/include/linux/futex.h
index 820125c628c1..34e54f2b8997 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -3,6 +3,8 @@
#include <linux/sched.h>
+union ktime;
+
/* Second argument to futex syscall */
@@ -94,7 +96,7 @@ struct robust_list_head {
#define ROBUST_LIST_LIMIT 2048
#ifdef __KERNEL__
-long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
+long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
u32 __user *uaddr2, u32 val2, u32 val3);
extern int
--
cgit v1.2.1