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>
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 50f24ee..dff27c4 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -141,24 +141,23 @@
struct compat_timespec __user *utime, u32 __user *uaddr2,
u32 val3)
{
- struct timespec t;
- unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
+ struct timespec ts;
+ ktime_t t, *tp = NULL;
int val2 = 0;
if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
- if (get_compat_timespec(&t, utime))
+ if (get_compat_timespec(&ts, utime))
return -EFAULT;
- if (!timespec_valid(&t))
+ if (!timespec_valid(&ts))
return -EINVAL;
+
+ t = timespec_to_ktime(ts);
if (op == FUTEX_WAIT)
- timeout = timespec_to_jiffies(&t) + 1;
- else {
- timeout = t.tv_sec;
- val2 = t.tv_nsec;
- }
+ t = ktime_add(ktime_get(), t);
+ tp = &t;
}
if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
val2 = (int) (unsigned long) utime;
- return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
+ return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}