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Make futex_wait() use an hrtimer for timeout

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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>
This commit is contained in:
Pierre Peiffer
2007-05-09 02:35:02 -07:00
committed by Linus Torvalds
parent ec92d08292
commit c19384b5b2
3 changed files with 56 additions and 54 deletions
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19
kernel/futex_compat.c
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@@ -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);
}