On Mon, 2019-03-11 at 13:52 +0800, Joyce Kong wrote:
> The spinlock implementation is unfair, some threads may take locks
> aggressively while leaving the other threads starving for long time.
>
> This patch introduces ticketlock which gives each waiting thread a
> ticket and they can take the lock one by one. First come, first
> serviced.
> This avoids starvation for too long time and is more predictable.
>
> Suggested-by: Jerin Jacob <jer...@marvell.com>
> Signed-off-by: Joyce kong <joyce.k...@arm.com>
> Reviewed-by: Gavin Hu <gavin...@arm.com>
> Reviewed-by: Ola Liljedahl <ola.liljed...@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> ---
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 097cfb4..12a091f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -210,6 +210,10 @@ M: Cristian Dumitrescu <
> cristian.dumitre...@intel.com>
> F: lib/librte_eal/common/include/rte_bitmap.h
> F: app/test/test_bitmap.c
>
> +Ticketlock
> +M: Joyce Kong <joyce.k...@arm.com>
> +F: lib/librte_eal/common/include/generic/rte_ticketlock.h
Add F: app/test/test_ticketlock.c in the next patch
>
> +#include <rte_lcore.h>
> +#include <rte_common.h>
> +#include <rte_pause.h>
Sort the header in alphabetical order.
> +
> +/**
> + * The rte_ticketlock_t type.
> + */
> +typedef struct {
> + uint16_t current;
> + uint16_t next;
> +} rte_ticketlock_t;
> +
>
> +
> +/**
> + * Take the ticketlock.
> + *
> + * @param tl
> + * A pointer to the ticketlock.
> + */
> +static inline __rte_experimental void
> +rte_ticketlock_lock(rte_ticketlock_t *tl)
> +{
> + unsigned int me = __atomic_fetch_add(&tl->next, 1,
If current, next is uint16_t why "me" as unsigned int.
> __ATOMIC_RELAXED);
> + while (__atomic_load_n(&tl->current, __ATOMIC_ACQUIRE) != me)
> + rte_pause();
> +}
> +
> +/**
> + * Release the ticketlock.
> + *
> + * @param tl
> + * A pointer to the ticketlock.
> + */
> +static inline __rte_experimental void
> +rte_ticketlock_unlock(rte_ticketlock_t *tl)
> +{
> + unsigned int i = __atomic_load_n(&tl->current,
> __ATOMIC_RELAXED);
> + i++;
You can save this line by making
__atomic_store_n(&tl->current, i + 1, __ATOMIC_RELEASE);
The code looks good. Please check the above comments and earlier
reported compilation issue with clang 7.1
