Re: [Minios-devel] [UNIKRAFT PATCH v3 07/10] plat/xen: Introduce Xenbus watch

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

Reviewed-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>

I will add one minor modification here (see inline)

Costin Lupu <costin.lupu@xxxxxxxxx> writes:

> Introduce the abstraction for Xenbus watches.
>
> Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
> ---
>  plat/xen/include/xenbus/client.h | 21 +++++++++++++++++++++
>  plat/xen/include/xenbus/xenbus.h | 16 ++++++++++++++++
>  plat/xen/xenbus/client.c         | 40 
> ++++++++++++++++++++++++++++++++++++++++
>  plat/xen/xenbus/exportsyms.uk    |  2 ++
>  4 files changed, 79 insertions(+)
>
> diff --git a/plat/xen/include/xenbus/client.h 
> b/plat/xen/include/xenbus/client.h
> index 964592d..f3540b7 100644
> --- a/plat/xen/include/xenbus/client.h
> +++ b/plat/xen/include/xenbus/client.h
> @@ -65,4 +65,25 @@ const char *xenbus_devtype_to_str(enum xenbus_dev_type 
> devtype);
>   */
>  enum xenbus_dev_type xenbus_str_to_devtype(const char *devtypestr);
>  
> +
> +/*
> + * Watches
> + */
> +
> +/*
> + * Waits for a watch event. Called by a client driver.
> + *
> + * @param watch Xenbus watch
> + * @return 0 on success, a negative errno value on error.
> + */
> +int xenbus_watch_wait_event(struct xenbus_watch *watch);
> +
> +/*
> + * Notifies a client driver waiting for watch events.
> + *
> + * @param watch Xenbus watch
> + * @return 0 on success, a negative errno value on error.
> + */
> +int xenbus_watch_notify_event(struct xenbus_watch *watch);
> +
>  #endif /* __XENBUS_CLIENT_H__ */
> diff --git a/plat/xen/include/xenbus/xenbus.h 
> b/plat/xen/include/xenbus/xenbus.h
> index 970b96a..230dcd4 100644
> --- a/plat/xen/include/xenbus/xenbus.h
> +++ b/plat/xen/include/xenbus/xenbus.h
> @@ -88,6 +88,22 @@ void _xenbus_register_driver(struct xenbus_driver *drv);
>  typedef unsigned long xenbus_transaction_t;
>  #define XBT_NIL ((xenbus_transaction_t) 0)
>  
> +/*
> + * Xenbus watch
> + */
> +
> +struct xenbus_watch {
> +     /**< in use internally */
> +     UK_TAILQ_ENTRY(struct xenbus_watch) watch_list;
> +     /**< Lock */
> +     spinlock_t lock;
> +     /**< Number of pending events */
> +     int pending_events;
> +     /**< Watch waiting queue */
> +     struct uk_waitq wq;
> +};
> +UK_TAILQ_HEAD(xenbus_watch_list, struct xenbus_watch);
> +
>  
>  /*
>   * Xenbus device
> diff --git a/plat/xen/xenbus/client.c b/plat/xen/xenbus/client.c
> index 3ddae5e..3dbca0f 100644
> --- a/plat/xen/xenbus/client.c
> +++ b/plat/xen/xenbus/client.c
> @@ -90,3 +90,43 @@ enum xenbus_dev_type xenbus_str_to_devtype(const char 
> *devtypestr)
>  
>       return xenbus_dev_none;
>  }
> +
> +/*
> + * Watches
> + */
> +
> +int xenbus_watch_wait_event(struct xenbus_watch *watch)
> +{
> +     if (watch == NULL)
> +             return -EINVAL;
> +
> +     while (1) {
> +             ukarch_spin_lock(&watch->lock);
> +
> +             if (watch->pending_events > 0)
> +                     break;
> +
> +             ukarch_spin_unlock(&watch->lock);
> +
> +             uk_waitq_wait_event(&watch->wq,
> +                     (watch->pending_events > 0));
> +     }
> +
> +     watch->pending_events--;
> +     ukarch_spin_unlock(&watch->lock);
> +
> +     return 0;
> +}
> +
> +int xenbus_watch_notify_event(struct xenbus_watch *watch)
> +{
> +     if (watch == NULL)
> +             return -EINVAL;
> +
> +     ukarch_spin_lock(&watch->lock);
> +     watch->pending_events++;
> +     uk_waitq_wake_up(&watch->wq);
> +     ukarch_spin_unlock(&watch->lock);
> +
> +     return 0;
> +}
> diff --git a/plat/xen/xenbus/exportsyms.uk b/plat/xen/xenbus/exportsyms.uk
> index e58bcf8..2352a82 100644
> --- a/plat/xen/xenbus/exportsyms.uk
> +++ b/plat/xen/xenbus/exportsyms.uk
> @@ -24,4 +24,6 @@ xs_get_self_id
>  xenbus_state_to_str
>  xenbus_devtype_to_str
>  xenbus_str_to_devtype
> +xenbus_watch_wait_event
> +xenbus_watch_notify_event
As discussed offline, notify_event is not needed to be exported. At
least for now. I will remove it from exportsyms.uk before pushing


>  
> -- 
> 2.11.0
>

-- 
Yuri Volchkov
Software Specialist

NEC Europe Ltd
Kurfürsten-Anlage 36
D-69115 Heidelberg

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