Re: [Minios-devel] [UNIKRAFT PATCH] lib/uksched: Make waiting queue act like actual queues

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

Hi Costin,

thanks for the patch. That behavior seems indeed much more sane.

Reviewed-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>

On 6/3/19 2:40 PM, Costin Lupu wrote:
> Waiting queues were used as stacks (LIFO) instead of queues (FIFO). The
> last added thread was the first one to be woken up which violates the
> fairness quality of waiting queues. This patch fixes that by adding the
> last added thread at the end of the queue.
>
> The pthread-embedded library provides a test which verifies this propery
> - the rwlock6 test.
>
> Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
> ---
>   lib/uksched/include/uk/wait.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/uksched/include/uk/wait.h b/lib/uksched/include/uk/wait.h
> index bf0e0c5c..94dae16f 100644
> --- a/lib/uksched/include/uk/wait.h
> +++ b/lib/uksched/include/uk/wait.h
> @@ -60,7 +60,7 @@ void uk_waitq_add(struct uk_waitq *wq,
>                 struct uk_waitq_entry *entry)
>   {
>         if (!entry->waiting) {
> -               UK_STAILQ_INSERT_HEAD(wq, entry, thread_list);
> +               UK_STAILQ_INSERT_TAIL(wq, entry, thread_list);
>                 entry->waiting = 1;
>         }
>   }
--
Dr. Florian Schmidt
フローリアン・シュミット
Research Scientist,
Systems and Machine Learning Group
NEC Laboratories Europe
Kurfürsten-Anlage 36, D-69115 Heidelberg
Tel.     +49 (0)6221 4342-265
Fax:     +49 (0)6221 4342-155
e-mail:  florian.schmidt@xxxxxxxxx
============================================================
Registered at Amtsgericht Mannheim, Germany, HRB728558

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