Re: [Xen-devel] [PATCH 04/22] libxl: Formally document libxl__xs_transaction

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-03-17 at 13:29 +0000, Ian Jackson wrote:
> Provide a more formal description of the semantics of
> libxl__xs_transaction_start, _commit and _abort, in addition to the
> usage pattern example.
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> ---
>  tools/libxl/libxl_internal.h |   20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 9e02861..60a39ed 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -626,6 +626,26 @@ int libxl__xs_rm_checked(libxl__gc *gc, xs_transaction_t 
> t, const char *path);
>   *        // other cleanups
>   *        return rc;
>   *    }
> + *
> + * Formally the states of *t are:
> + *
> + *  name     value of *t  description
> + *   Idle         0         no transaction exists
> + *   Ready        non-0     ready for work, nothing done yet
> + *   Busy         non-0     writes have been made but we are not finished
> + *   Uncommitted  non-0     writes have been made and should be committed
> + *
> + * libxl__xs_transaction_start:  Idle -> Ready (on error: Idle)
> + *
> + * The transaction goes from Ready to Busy, and from Busy to
> + * Uncommitted, by the use of xenstore read and write operations
> + * (libxl__xs_..., xs_...) made by libxl__xs_transaction's caller.
> + *
> + * libxl__xs_transaction_commit:  Ready/Uncommitted -> Idle
> + *     on success (returns 0): xenstore has been updated
> + *     on error (<0) or conflict (+1): updates discarded
> + *
> + * libxl__xs_transaction_abort:  Any -> Idle  (any updates discarded)
>   */
>  int libxl__xs_transaction_start(libxl__gc *gc, xs_transaction_t *t);
>  int libxl__xs_transaction_commit(libxl__gc *gc, xs_transaction_t *t);



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