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authorPierre Peiffer <pierre.peiffer@bull.net>2007-05-09 02:35:02 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:55 -0700
commitc19384b5b296905d4988c7c684ff540a0f9d65be (patch)
tree071cfe0855d409d63de80ec1b9b663738efb09de /kernel/futex_compat.c
parentec92d08292d3e9b0823eba138a4564d2d39f25c7 (diff)
downloadlinaro-lsk-c19384b5b296905d4988c7c684ff540a0f9d65be.tar.gz
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>
Diffstat (limited to 'kernel/futex_compat.c')
-rw-r--r--kernel/futex_compat.c19
1 files changed, 9 insertions, 10 deletions
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 50f24eea6cd..dff27c471ea 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -141,24 +141,23 @@ asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
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);
}