Thomas Gleixner <[email protected]> wrote:
>
>
> Replace the nanosleep private sleeper functionality by the generic
> hrtimer sleeper.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Signed-off-by: Ingo Molnar <[email protected]>
>
>
> kernel/hrtimer.c | 34 +++++++---------------------------
> 1 file changed, 7 insertions(+), 27 deletions(-)
>
> Index: linux-2.6.16/kernel/hrtimer.c
> ===================================================================
> --- linux-2.6.16.orig/kernel/hrtimer.c
> +++ linux-2.6.16/kernel/hrtimer.c
> @@ -655,7 +655,6 @@ void hrtimer_run_queues(void)
> /*
> * Sleep related functions:
> */
> -
> static int hrtimer_wakeup(struct hrtimer *timer)
> {
> struct hrtimer_sleeper *t =
> @@ -675,28 +674,9 @@ void hrtimer_init_sleeper(struct hrtimer
> sl->task = task;
> }
>
> -struct sleep_hrtimer {
> - struct hrtimer timer;
> - struct task_struct *task;
> - int expired;
> -};
> -
> -static int nanosleep_wakeup(struct hrtimer *timer)
> -{
> - struct sleep_hrtimer *t =
> - container_of(timer, struct sleep_hrtimer, timer);
> -
> - t->expired = 1;
> - wake_up_process(t->task);
> -
> - return HRTIMER_NORESTART;
> -}
> -
> -static int __sched do_nanosleep(struct sleep_hrtimer *t, enum hrtimer_mode mode)
> +static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
> {
> - t->timer.function = nanosleep_wakeup;
> - t->task = current;
> - t->expired = 0;
> + hrtimer_init_sleeper(t, current);
>
> do {
> set_current_state(TASK_INTERRUPTIBLE);
> @@ -704,18 +684,18 @@ static int __sched do_nanosleep(struct s
>
> schedule();
>
> - if (unlikely(!t->expired)) {
> + if (unlikely(t->task)) {
> hrtimer_cancel(&t->timer);
> mode = HRTIMER_ABS;
> }
> - } while (!t->expired && !signal_pending(current));
> + } while (t->task && !signal_pending(current));
>
> - return t->expired;
> + return t->task == NULL;
> }
This all looks vaguely racy. hrtimer_wakeup() will set t->task to NULL
without barriers, locks or anything. And the waiter here can break out of
schedule() due to signal delivery while a wakeup is in progress.
So the value of t->task here is fairly meaningless. Ot just depends on how
far the waker has got through hrtimer_wakeup().
Maybe that doesn't matter, because hrtimer_cancel() will spin until
hrtimer_wakeup() has completed anyway, but could you please recheck and
confirm that this is all solid?
-
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