Re: [Xen-devel] [PATCH 23/28] libxl: ocaml: allow device operations to be called asynchronously

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-03-25 at 14:45 +0000, Rob Hoes wrote:
> Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
> ---
>  tools/ocaml/libs/xl/genwrap.py       |    6 +++---
>  tools/ocaml/libs/xl/xenlight_stubs.c |   19 ++++++++++++++++---
>  2 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/ocaml/libs/xl/genwrap.py b/tools/ocaml/libs/xl/genwrap.py
> index 10e6a74..9f7895a 100644
> --- a/tools/ocaml/libs/xl/genwrap.py
> +++ b/tools/ocaml/libs/xl/genwrap.py
> @@ -22,9 +22,9 @@ builtins = {
>      "libxl_cpuid_policy_list": ("unit",                "%(c)s = 0",          
>                "Val_unit"),
>      }
>  
> -DEVICE_FUNCTIONS = [ ("add",            ["ctx", "t", "domid", "unit"]),
> -                     ("remove",         ["ctx", "t", "domid", "unit"]),
> -                     ("destroy",        ["ctx", "t", "domid", "unit"]),
> +DEVICE_FUNCTIONS = [ ("add",            ["ctx", "?async:'a", "t", "domid", 
> "unit"]),
> +                     ("remove",         ["ctx", "?async:'a", "t", "domid", 
> "unit"]),
> +                     ("destroy",        ["ctx", "?async:'a", "t", "domid", 
> "unit"]),
>                     ]
>  
>  functions = { # ( name , [type1,type2,....] )
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c 
> b/tools/ocaml/libs/xl/xenlight_stubs.c
> index ae5317f..c136db7 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -338,17 +338,30 @@ void async_callback(libxl_ctx *ctx, int rc, void 
> *for_callback)
>  #define STRINGIFY(x) _STRINGIFY(x)
>  
>  #define _DEVICE_ADDREMOVE(type,op)                                   \
> -value stub_xl_device_##type##_##op(value ctx, value info, value domid)       
> \
> +value stub_xl_device_##type##_##op(value ctx, value async, value info,       
> \
> +     value domid)                                                    \
>  {                                                                    \
> -     CAMLparam3(ctx, info, domid);                                   \
> +     CAMLparam4(ctx, info, domid, async);                            \
>       libxl_device_##type c_info;                                     \
>       int ret, marker_var;                                            \
> +     libxl_asyncop_how *ao_how;                                      \
>                                                                       \
>       device_##type##_val(CTX, &c_info, info);                        \
>                                                                       \
> -     ret = libxl_device_##type##_##op(CTX, Int_val(domid), &c_info, 0); \
> +     if (async != Val_none) {                                        \
> +             ao_how = malloc(sizeof(*ao_how));                       \

libxl.h says:
 * *ao_how does not need to remain valid after the initiating function
 * returns. All other parameters must remain valid for the lifetime of
 * the asynchronous operation, unless otherwise specified.

So the ao_how can just be a normal stack variable if you like. If you
want to use NULL/non-NULL-ness to indicate Some/None then:
        struct ao_how aoh_struct, *aoh = NULL;
        if (async != Val_none)
                aoh = &aoh_struct
works I think or just 
        struct ao_how aoh = { .callback = async_callback, ... };

        ret = libxl_device_##type##_##op(CTX, Int_val(domid), &c_info,  \
                                         async != Val_none ? &aoh : NULL
would do.

> +             ao_how->callback = async_callback;                      \
> +             ao_how->u.for_callback = (void *) Some_val(async);      \
> +     }                                                               \
> +     else                                                            \
> +             ao_how = NULL;                                          \
> +                                                                     \
> +     ret = libxl_device_##type##_##op(CTX, Int_val(domid), &c_info,  \
> +             ao_how);                                                \
>                                                                       \
>       libxl_device_##type##_dispose(&c_info);                         \
> +     if (ao_how)                                                     \
> +             free(ao_how);                                           \
>                                                                       \
>       if (ret != 0)                                                   \
>               failwith_xl(ret, STRINGIFY(type) "_" STRINGIFY(op));    \



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