Re: [Minios-devel] [UNIKRAFT PATCH] lib/ukmpi: Provide blocking uk_mbox_recv()

[Costin Lupu <costin.lup@xxxxxxxxx>]

Hi Simon,

This patch looks good.

Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>

On 5/8/19 1:27 AM, Simon Kuenzer wrote:
> Commit a48d634 ("lib/uklock: Use timeout equal to 0 for trying down a
> semaphore") implicitly changed the behavior of `uk_mbox_recv_to()`. When
> passing timeout `0`, the function is not blocking until a message
> arrives but trying to receive a message and returning immediately.
> 
> This patch introduces `uk_mbox_recv()` which brings back this blocking
> behavior. I chose introducing this new function in order to keep the
> mailbox API inline with the semaphore ones.
> 
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
>  lib/ukmpi/exportsyms.uk     |  1 +
>  lib/ukmpi/include/uk/mbox.h |  1 +
>  lib/ukmpi/mbox.c            | 17 +++++++++++++++++
>  3 files changed, 19 insertions(+)
> 
> diff --git a/lib/ukmpi/exportsyms.uk b/lib/ukmpi/exportsyms.uk
> index 4c4c8874..b0d661a0 100644
> --- a/lib/ukmpi/exportsyms.uk
> +++ b/lib/ukmpi/exportsyms.uk
> @@ -3,5 +3,6 @@ uk_mbox_free
>  uk_mbox_post
>  uk_mbox_post_try
>  uk_mbox_post_to
> +uk_mbox_recv
>  uk_mbox_recv_try
>  uk_mbox_recv_to
> diff --git a/lib/ukmpi/include/uk/mbox.h b/lib/ukmpi/include/uk/mbox.h
> index d2c48e53..19b1ecc0 100644
> --- a/lib/ukmpi/include/uk/mbox.h
> +++ b/lib/ukmpi/include/uk/mbox.h
> @@ -56,6 +56,7 @@ void uk_mbox_post(struct uk_mbox *m, void *msg);
>  int uk_mbox_post_try(struct uk_mbox *m, void *msg);
>  __nsec uk_mbox_post_to(struct uk_mbox *m, void *msg, __nsec timeout);
>  
> +void uk_mbox_recv(struct uk_mbox *m, void **msg);
>  int uk_mbox_recv_try(struct uk_mbox *m, void **msg);
>  __nsec uk_mbox_recv_to(struct uk_mbox *m, void **msg, __nsec timeout);
>  
> diff --git a/lib/ukmpi/mbox.c b/lib/ukmpi/mbox.c
> index 3a0354dd..149a667d 100644
> --- a/lib/ukmpi/mbox.c
> +++ b/lib/ukmpi/mbox.c
> @@ -127,6 +127,23 @@ static inline void *_do_mbox_recv(struct uk_mbox *m)
>       return ret;
>  }
>  
> +/* Blocks the thread until a message arrives in the mailbox.
> + * The `*msg` argument will point to the received message.
> + * If the `msg` parameter was set to NULL, the received message is dropped.
> + */
> +void uk_mbox_recv(struct uk_mbox *m, void **msg)
> +{
> +     void *rmsg;
> +
> +     UK_ASSERT(m);
> +
> +     uk_semaphore_down(&m->readsem);
> +     rmsg =  _do_mbox_recv(m);
> +     if (msg)
> +             *msg = rmsg;
> +}
> +
> +
>  /* This is similar to uk_mbox_fetch, however if a message is not
>   * present in the mailbox, it immediately returns with the code
>   * SYS_MBOX_EMPTY. On success 0 is returned.
> 

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