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DateTue, 6 Apr 2010 10:27:58 +0200 (CEST)
FromThomas Gleixner <>
SubjectRe: [PATCH 5/6] futex: handle timeout inside adaptive lock spin
On Mon, 5 Apr 2010, Darren Hart wrote:

> Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
> ---
> kernel/futex.c | 24 +++++++++++++++++++++---
> 1 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index c33ac2a..af61dcd 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2385,6 +2385,7 @@ out:
> /**
> * trylock_futex_adaptive() - Try to acquire the futex lock in a busy loop
> * @uaddr: the futex user address
> + * @timeout: absolute timeout or NULL if none
> *
> * Try to acquire a futex lock in a loop until the owner changes or the owner
> * is descheduled. To lock the futex, set the value to the current TID.
> @@ -2394,10 +2395,11 @@ out:
> * 1 - Futex lock acquired
> * <0 - On error
> */
> -static int trylock_futex_adaptive(u32 __user *uaddr)
> +static int trylock_futex_adaptive(u32 __user *uaddr, ktime_t *timeout)
> {
> int ret = 0;
> u32 curval;
> + ktime_t now;
>
> for (;;) {
> struct thread_info *owner;
> @@ -2433,6 +2435,22 @@ static int trylock_futex_adaptive(u32 __user *uaddr)
> if (need_resched())
> break;
>
> + if (timeout) {
> + now = ktime_get();

Hmm. Calling that in every iteration might hurt especially on non
TSC systems, but well...

> +/* FIXME: consider creating ktime_less_than(lhs, rhs) */

No need. The .tv64 comparison works in both cases. :)

Thanks,

tglx


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