Eric Blake
2019-Aug-15 21:52 UTC
[Libguestfs] [nbdkit PATCH] ocaml: Add support for dynamic .thread_model
We do not promise API stability for non-C languages; this is an API
break as follows: instead of calling 'NBDKit.register_plugin model
plugin' with a static model, you can now add .thread_model :(unit ->
thread_model) to plugin or default to PARALLEL.
Since all existing OCaml plugins will have already thought about
thread models, they can convert their existing model into the new
plugin field (and thus, I don't feel too bad making PARALLEL the
default, even if it is not always the safest).
Signed-off-by: Eric Blake <eblake@redhat.com>
---
I'm still looking at two followups:
1) ./nbdkit doesn't set LD_LIBRARY_PATH=plugins/ocaml/.libs:$LD_LIBRARY_PATH
(making ./nbdkit --dump-plugin tests/test-ocaml-plugin.so fail to load
when the system nbdkit is too old)
2) although --dump-plugin shows thread model, ./nbdkit -v log does not;
I need to add a debug() statement for that in server/locks.c
But I was quite pleased that I got this working in under 3 hours (I'm
getting better at OCaml).
plugins/ocaml/nbdkit-ocaml-plugin.pod | 13 ++++++-----
plugins/ocaml/ocaml.c | 33 +++++++++++++++++++++------
plugins/ocaml/NBDKit.ml | 28 ++++++++++++++---------
plugins/ocaml/NBDKit.mli | 19 ++++++++-------
plugins/ocaml/example.ml | 9 +++++---
tests/test_ocaml_plugin.ml | 5 ++--
6 files changed, 69 insertions(+), 38 deletions(-)
diff --git a/plugins/ocaml/nbdkit-ocaml-plugin.pod
b/plugins/ocaml/nbdkit-ocaml-plugin.pod
index a66cf26e..4b349612 100644
--- a/plugins/ocaml/nbdkit-ocaml-plugin.pod
+++ b/plugins/ocaml/nbdkit-ocaml-plugin.pod
@@ -36,12 +36,11 @@ Your OCaml code should call C<NBDKit.register_plugin>
like this:
open_connection = Some myplugin_open;
get_size = Some myplugin_get_size;
pread = Some myplugin_pread;
+ thread_model = Some (fun () ->
NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS);
(* etc *)
}
- let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS
-
- let () = NBDKit.register_plugin thread_model plugin
+ let () = NBDKit.register_plugin plugin
Your plugin must call C<register_plugin> exactly once when the plugin
is loaded.
@@ -108,9 +107,11 @@ to control this.
=head2 Threads
-The first parameter of C<NBDKit.register_plugin> is the thread model,
-which can be one of the values in the table below. For more
-information on thread models, see L<nbdkit-plugin(3)/THREADS>. Note
+One of the members in the plugin record passed to
+C<NBDKit.register_plugin> is C<thread model>, which must return one
of
+the values in the table below. For more information on thread models,
+see L<nbdkit-plugin(3)/THREADS>. If this optional function is not
+provided, the thread model defaults to THREAD_MODEL_PARALLEL. Note
that because of the garbage collector lock in OCaml, callbacks are
never truly concurrent.
diff --git a/plugins/ocaml/ocaml.c b/plugins/ocaml/ocaml.c
index f664a7fb..01f4448f 100644
--- a/plugins/ocaml/ocaml.c
+++ b/plugins/ocaml/ocaml.c
@@ -72,6 +72,7 @@ static void remove_roots (void);
static struct nbdkit_plugin plugin = {
._struct_size = sizeof (plugin),
._api_version = NBDKIT_API_VERSION,
+ ._thread_model = NBDKIT_THREAD_MODEL_PARALLEL,
/* The following field is used as a canary to detect whether the
* OCaml code started up and called us back successfully. If it's
@@ -131,6 +132,8 @@ static value extents_fn;
static value can_cache_fn;
static value cache_fn;
+static value thread_model_fn;
+
/*----------------------------------------------------------------------*/
/* Wrapper functions that translate calls from C (ie. nbdkit) to OCaml. */
@@ -683,18 +686,30 @@ cache_wrapper (void *h, uint32_t count, uint64_t offset,
uint32_t flags)
CAMLreturnT (int, 0);
}
+static int
+thread_model_wrapper (void)
+{
+ CAMLparam0 ();
+ CAMLlocal1 (rv);
+
+ caml_leave_blocking_section ();
+
+ rv = caml_callback_exn (config_complete_fn, Val_unit);
+ if (Is_exception_result (rv)) {
+ nbdkit_error ("%s", caml_format_exception (Extract_exception
(rv)));
+ caml_enter_blocking_section ();
+ CAMLreturnT (int, -1);
+ }
+
+ caml_enter_blocking_section ();
+ CAMLreturnT (int, Int_val (rv));
+}
+
/*----------------------------------------------------------------------*/
/* set_* functions called from OCaml code at load time to initialize
* fields in the plugin struct.
*/
-value
-ocaml_nbdkit_set_thread_model (value modelv)
-{
- plugin._thread_model = Int_val (modelv);
- return Val_unit;
-}
-
value
ocaml_nbdkit_set_name (value namev)
{
@@ -775,6 +790,8 @@ SET(extents)
SET(can_cache)
SET(cache)
+SET(thread_model)
+
#undef SET
static void
@@ -817,6 +834,8 @@ remove_roots (void)
REMOVE (can_cache);
REMOVE (cache);
+ REMOVE (thread_model);
+
#undef REMOVE
}
diff --git a/plugins/ocaml/NBDKit.ml b/plugins/ocaml/NBDKit.ml
index 02aa2001..57e57a46 100644
--- a/plugins/ocaml/NBDKit.ml
+++ b/plugins/ocaml/NBDKit.ml
@@ -1,3 +1,4 @@
+(* hey emacs, this is OCaml code: -*- tuareg -*- *)
(* nbdkit OCaml interface
* Copyright (C) 2014-2019 Red Hat Inc.
*
@@ -39,6 +40,12 @@ type fua_flag = FuaNone | FuaEmulate | FuaNative
type cache_flag = CacheNone | CacheEmulate | CacheNop
+type thread_model +| THREAD_MODEL_SERIALIZE_CONNECTIONS
+| THREAD_MODEL_SERIALIZE_ALL_REQUESTS
+| THREAD_MODEL_SERIALIZE_REQUESTS
+| THREAD_MODEL_PARALLEL
+
type extent = {
offset : int64;
length : int64;
@@ -87,6 +94,8 @@ type 'a plugin = {
can_cache : ('a -> cache_flag) option;
cache : ('a -> int32 -> int64 -> flags -> unit) option;
+
+ thread_model : (unit -> thread_model) option;
}
let default_callbacks = {
@@ -130,16 +139,10 @@ let default_callbacks = {
can_cache = None;
cache = None;
+
+ thread_model = None;
}
-type thread_model -| THREAD_MODEL_SERIALIZE_CONNECTIONS
-| THREAD_MODEL_SERIALIZE_ALL_REQUESTS
-| THREAD_MODEL_SERIALIZE_REQUESTS
-| THREAD_MODEL_PARALLEL
-
-external set_thread_model : int -> unit =
"ocaml_nbdkit_set_thread_model" "noalloc"
-
external set_name : string -> unit = "ocaml_nbdkit_set_name"
"noalloc"
external set_longname : string -> unit =
"ocaml_nbdkit_set_longname" "noalloc"
external set_version : string -> unit = "ocaml_nbdkit_set_version"
"noalloc"
@@ -181,9 +184,11 @@ external set_extents : ('a -> int32 -> int64
-> flags -> extent list) -> unit external set_can_cache : ('a
-> cache_flag) -> unit = "ocaml_nbdkit_set_can_cache"
external set_cache : ('a -> int32 -> int64 -> flags -> unit)
-> unit = "ocaml_nbdkit_set_cache"
+external set_thread_model : (unit -> thread_model) -> unit =
"ocaml_nbdkit_set_thread_model" "noalloc"
+
let may f = function None -> () | Some a -> f a
-let register_plugin thread_model plugin +let register_plugin plugin (* Check
the required fields have been set by the caller. *)
if plugin.name = "" then
failwith "'.name' field in NBDKit.plugin structure must be
set";
@@ -198,7 +203,6 @@ let register_plugin thread_model plugin
plugin.name);
(* Set the fields in the C code. *)
- set_thread_model (Obj.magic thread_model);
set_name plugin.name;
if plugin.longname <> "" then
@@ -243,7 +247,9 @@ let register_plugin thread_model plugin may set_extents
plugin.extents;
may set_can_cache plugin.can_cache;
- may set_cache plugin.cache
+ may set_cache plugin.cache;
+
+ may set_thread_model plugin.thread_model
external _set_error : int -> unit = "ocaml_nbdkit_set_error"
"noalloc"
diff --git a/plugins/ocaml/NBDKit.mli b/plugins/ocaml/NBDKit.mli
index bab8f7f6..778250ef 100644
--- a/plugins/ocaml/NBDKit.mli
+++ b/plugins/ocaml/NBDKit.mli
@@ -1,3 +1,4 @@
+(* hey emacs, this is OCaml code: -*- tuareg -*- *)
(* nbdkit OCaml interface
* Copyright (C) 2014-2019 Red Hat Inc.
*
@@ -50,6 +51,13 @@ type extent = {
}
(** The type of the extent list returned by [.extents]. *)
+type thread_model +| THREAD_MODEL_SERIALIZE_CONNECTIONS
+| THREAD_MODEL_SERIALIZE_ALL_REQUESTS
+| THREAD_MODEL_SERIALIZE_REQUESTS
+| THREAD_MODEL_PARALLEL
+(** The type of the thread model returned by [.thread_model]. *)
+
type 'a plugin = {
name : string; (* required *)
longname : string;
@@ -91,6 +99,8 @@ type 'a plugin = {
can_cache : ('a -> cache_flag) option;
cache : ('a -> int32 -> int64 -> flags -> unit) option;
+
+ thread_model : (unit -> thread_model) option;
}
(** The plugin fields and callbacks. ['a] is the handle type. *)
@@ -98,14 +108,7 @@ val default_callbacks : 'a plugin
(** The plugin with all fields set to [None], so you can write
[{ defaults_callbacks with field1 = Some foo1; field2 = Some foo2 }] *)
-type thread_model -| THREAD_MODEL_SERIALIZE_CONNECTIONS
-| THREAD_MODEL_SERIALIZE_ALL_REQUESTS
-| THREAD_MODEL_SERIALIZE_REQUESTS
-| THREAD_MODEL_PARALLEL
-(** The thread model. *)
-
-val register_plugin : thread_model -> 'a plugin -> unit
+val register_plugin : 'a plugin -> unit
(** Register the plugin with nbdkit. *)
val set_error : Unix.error -> unit
diff --git a/plugins/ocaml/example.ml b/plugins/ocaml/example.ml
index 8ec6f063..45de035f 100644
--- a/plugins/ocaml/example.ml
+++ b/plugins/ocaml/example.ml
@@ -71,6 +71,9 @@ let ocamlexample_pwrite h buf offset _ let offset =
Int64.to_int offset in
String.blit buf 0 !disk offset len
+let ocamlexample_thread_model () + NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS
+
let plugin = {
NBDKit.default_callbacks with
(* name, open_connection, get_size and pread are required,
@@ -88,8 +91,8 @@ let plugin = {
get_size = Some ocamlexample_get_size;
pread = Some ocamlexample_pread;
pwrite = Some ocamlexample_pwrite;
+
+ thread_model = Some ocamlexample_thread_model;
}
-let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS
-
-let () = NBDKit.register_plugin thread_model plugin
+let () = NBDKit.register_plugin plugin
diff --git a/tests/test_ocaml_plugin.ml b/tests/test_ocaml_plugin.ml
index eb0d9319..3cf8fd90 100644
--- a/tests/test_ocaml_plugin.ml
+++ b/tests/test_ocaml_plugin.ml
@@ -75,8 +75,7 @@ let plugin = {
pwrite = Some test_pwrite;
extents = Some test_extents;
+ thread_model = Some (fun () ->
NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS);
}
-let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS
-
-let () = NBDKit.register_plugin thread_model plugin
+let () = NBDKit.register_plugin plugin
--
2.20.1
Richard W.M. Jones
2019-Aug-15 21:59 UTC
Re: [Libguestfs] [nbdkit PATCH] ocaml: Add support for dynamic .thread_model
On Thu, Aug 15, 2019 at 04:52:00PM -0500, Eric Blake wrote:> We do not promise API stability for non-C languages; this is an API > break as follows: instead of calling 'NBDKit.register_plugin model > plugin' with a static model, you can now add .thread_model :(unit -> > thread_model) to plugin or default to PARALLEL. > > Since all existing OCaml plugins will have already thought about > thread models, they can convert their existing model into the new > plugin field (and thus, I don't feel too bad making PARALLEL the > default, even if it is not always the safest). > > Signed-off-by: Eric Blake <eblake@redhat.com>Patch looks OK. It would crash pretty early if there was something wrong in the bindings, so ACK.> I'm still looking at two followups: > 1) ./nbdkit doesn't set LD_LIBRARY_PATH=plugins/ocaml/.libs:$LD_LIBRARY_PATH > (making ./nbdkit --dump-plugin tests/test-ocaml-plugin.so fail to load > when the system nbdkit is too old)Yes this is surely a bug. After making that change the line can also be removed from tests/Makefile.am.> 2) although --dump-plugin shows thread model, ./nbdkit -v log does not; > I need to add a debug() statement for that in server/locks.cYes I guess it's a good idea to add it to the debug output. Helps with checking that we really got the intended thread model in all circumstances. Thanks, Rich.> But I was quite pleased that I got this working in under 3 hours (I'm > getting better at OCaml). > > plugins/ocaml/nbdkit-ocaml-plugin.pod | 13 ++++++----- > plugins/ocaml/ocaml.c | 33 +++++++++++++++++++++------ > plugins/ocaml/NBDKit.ml | 28 ++++++++++++++--------- > plugins/ocaml/NBDKit.mli | 19 ++++++++------- > plugins/ocaml/example.ml | 9 +++++--- > tests/test_ocaml_plugin.ml | 5 ++-- > 6 files changed, 69 insertions(+), 38 deletions(-) > > diff --git a/plugins/ocaml/nbdkit-ocaml-plugin.pod b/plugins/ocaml/nbdkit-ocaml-plugin.pod > index a66cf26e..4b349612 100644 > --- a/plugins/ocaml/nbdkit-ocaml-plugin.pod > +++ b/plugins/ocaml/nbdkit-ocaml-plugin.pod > @@ -36,12 +36,11 @@ Your OCaml code should call C<NBDKit.register_plugin> like this: > open_connection = Some myplugin_open; > get_size = Some myplugin_get_size; > pread = Some myplugin_pread; > + thread_model = Some (fun () -> NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS); > (* etc *) > } > > - let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS > - > - let () = NBDKit.register_plugin thread_model plugin > + let () = NBDKit.register_plugin plugin > > Your plugin must call C<register_plugin> exactly once when the plugin > is loaded. > @@ -108,9 +107,11 @@ to control this. > > =head2 Threads > > -The first parameter of C<NBDKit.register_plugin> is the thread model, > -which can be one of the values in the table below. For more > -information on thread models, see L<nbdkit-plugin(3)/THREADS>. Note > +One of the members in the plugin record passed to > +C<NBDKit.register_plugin> is C<thread model>, which must return one of > +the values in the table below. For more information on thread models, > +see L<nbdkit-plugin(3)/THREADS>. If this optional function is not > +provided, the thread model defaults to THREAD_MODEL_PARALLEL. Note > that because of the garbage collector lock in OCaml, callbacks are > never truly concurrent. > > diff --git a/plugins/ocaml/ocaml.c b/plugins/ocaml/ocaml.c > index f664a7fb..01f4448f 100644 > --- a/plugins/ocaml/ocaml.c > +++ b/plugins/ocaml/ocaml.c > @@ -72,6 +72,7 @@ static void remove_roots (void); > static struct nbdkit_plugin plugin = { > ._struct_size = sizeof (plugin), > ._api_version = NBDKIT_API_VERSION, > + ._thread_model = NBDKIT_THREAD_MODEL_PARALLEL, > > /* The following field is used as a canary to detect whether the > * OCaml code started up and called us back successfully. If it's > @@ -131,6 +132,8 @@ static value extents_fn; > static value can_cache_fn; > static value cache_fn; > > +static value thread_model_fn; > + > /*----------------------------------------------------------------------*/ > /* Wrapper functions that translate calls from C (ie. nbdkit) to OCaml. */ > > @@ -683,18 +686,30 @@ cache_wrapper (void *h, uint32_t count, uint64_t offset, uint32_t flags) > CAMLreturnT (int, 0); > } > > +static int > +thread_model_wrapper (void) > +{ > + CAMLparam0 (); > + CAMLlocal1 (rv); > + > + caml_leave_blocking_section (); > + > + rv = caml_callback_exn (config_complete_fn, Val_unit); > + if (Is_exception_result (rv)) { > + nbdkit_error ("%s", caml_format_exception (Extract_exception (rv))); > + caml_enter_blocking_section (); > + CAMLreturnT (int, -1); > + } > + > + caml_enter_blocking_section (); > + CAMLreturnT (int, Int_val (rv)); > +} > + > /*----------------------------------------------------------------------*/ > /* set_* functions called from OCaml code at load time to initialize > * fields in the plugin struct. > */ > > -value > -ocaml_nbdkit_set_thread_model (value modelv) > -{ > - plugin._thread_model = Int_val (modelv); > - return Val_unit; > -} > - > value > ocaml_nbdkit_set_name (value namev) > { > @@ -775,6 +790,8 @@ SET(extents) > SET(can_cache) > SET(cache) > > +SET(thread_model) > + > #undef SET > > static void > @@ -817,6 +834,8 @@ remove_roots (void) > REMOVE (can_cache); > REMOVE (cache); > > + REMOVE (thread_model); > + > #undef REMOVE > } > > diff --git a/plugins/ocaml/NBDKit.ml b/plugins/ocaml/NBDKit.ml > index 02aa2001..57e57a46 100644 > --- a/plugins/ocaml/NBDKit.ml > +++ b/plugins/ocaml/NBDKit.ml > @@ -1,3 +1,4 @@ > +(* hey emacs, this is OCaml code: -*- tuareg -*- *) > (* nbdkit OCaml interface > * Copyright (C) 2014-2019 Red Hat Inc. > * > @@ -39,6 +40,12 @@ type fua_flag = FuaNone | FuaEmulate | FuaNative > > type cache_flag = CacheNone | CacheEmulate | CacheNop > > +type thread_model > +| THREAD_MODEL_SERIALIZE_CONNECTIONS > +| THREAD_MODEL_SERIALIZE_ALL_REQUESTS > +| THREAD_MODEL_SERIALIZE_REQUESTS > +| THREAD_MODEL_PARALLEL > + > type extent = { > offset : int64; > length : int64; > @@ -87,6 +94,8 @@ type 'a plugin = { > > can_cache : ('a -> cache_flag) option; > cache : ('a -> int32 -> int64 -> flags -> unit) option; > + > + thread_model : (unit -> thread_model) option; > } > > let default_callbacks = { > @@ -130,16 +139,10 @@ let default_callbacks = { > > can_cache = None; > cache = None; > + > + thread_model = None; > } > > -type thread_model > -| THREAD_MODEL_SERIALIZE_CONNECTIONS > -| THREAD_MODEL_SERIALIZE_ALL_REQUESTS > -| THREAD_MODEL_SERIALIZE_REQUESTS > -| THREAD_MODEL_PARALLEL > - > -external set_thread_model : int -> unit = "ocaml_nbdkit_set_thread_model" "noalloc" > - > external set_name : string -> unit = "ocaml_nbdkit_set_name" "noalloc" > external set_longname : string -> unit = "ocaml_nbdkit_set_longname" "noalloc" > external set_version : string -> unit = "ocaml_nbdkit_set_version" "noalloc" > @@ -181,9 +184,11 @@ external set_extents : ('a -> int32 -> int64 -> flags -> extent list) -> unit > external set_can_cache : ('a -> cache_flag) -> unit = "ocaml_nbdkit_set_can_cache" > external set_cache : ('a -> int32 -> int64 -> flags -> unit) -> unit = "ocaml_nbdkit_set_cache" > > +external set_thread_model : (unit -> thread_model) -> unit = "ocaml_nbdkit_set_thread_model" "noalloc" > + > let may f = function None -> () | Some a -> f a > > -let register_plugin thread_model plugin > +let register_plugin plugin > (* Check the required fields have been set by the caller. *) > if plugin.name = "" then > failwith "'.name' field in NBDKit.plugin structure must be set"; > @@ -198,7 +203,6 @@ let register_plugin thread_model plugin > plugin.name); > > (* Set the fields in the C code. *) > - set_thread_model (Obj.magic thread_model); > > set_name plugin.name; > if plugin.longname <> "" then > @@ -243,7 +247,9 @@ let register_plugin thread_model plugin > may set_extents plugin.extents; > > may set_can_cache plugin.can_cache; > - may set_cache plugin.cache > + may set_cache plugin.cache; > + > + may set_thread_model plugin.thread_model > > external _set_error : int -> unit = "ocaml_nbdkit_set_error" "noalloc" > > diff --git a/plugins/ocaml/NBDKit.mli b/plugins/ocaml/NBDKit.mli > index bab8f7f6..778250ef 100644 > --- a/plugins/ocaml/NBDKit.mli > +++ b/plugins/ocaml/NBDKit.mli > @@ -1,3 +1,4 @@ > +(* hey emacs, this is OCaml code: -*- tuareg -*- *) > (* nbdkit OCaml interface > * Copyright (C) 2014-2019 Red Hat Inc. > * > @@ -50,6 +51,13 @@ type extent = { > } > (** The type of the extent list returned by [.extents]. *) > > +type thread_model > +| THREAD_MODEL_SERIALIZE_CONNECTIONS > +| THREAD_MODEL_SERIALIZE_ALL_REQUESTS > +| THREAD_MODEL_SERIALIZE_REQUESTS > +| THREAD_MODEL_PARALLEL > +(** The type of the thread model returned by [.thread_model]. *) > + > type 'a plugin = { > name : string; (* required *) > longname : string; > @@ -91,6 +99,8 @@ type 'a plugin = { > > can_cache : ('a -> cache_flag) option; > cache : ('a -> int32 -> int64 -> flags -> unit) option; > + > + thread_model : (unit -> thread_model) option; > } > (** The plugin fields and callbacks. ['a] is the handle type. *) > > @@ -98,14 +108,7 @@ val default_callbacks : 'a plugin > (** The plugin with all fields set to [None], so you can write > [{ defaults_callbacks with field1 = Some foo1; field2 = Some foo2 }] *) > > -type thread_model > -| THREAD_MODEL_SERIALIZE_CONNECTIONS > -| THREAD_MODEL_SERIALIZE_ALL_REQUESTS > -| THREAD_MODEL_SERIALIZE_REQUESTS > -| THREAD_MODEL_PARALLEL > -(** The thread model. *) > - > -val register_plugin : thread_model -> 'a plugin -> unit > +val register_plugin : 'a plugin -> unit > (** Register the plugin with nbdkit. *) > > val set_error : Unix.error -> unit > diff --git a/plugins/ocaml/example.ml b/plugins/ocaml/example.ml > index 8ec6f063..45de035f 100644 > --- a/plugins/ocaml/example.ml > +++ b/plugins/ocaml/example.ml > @@ -71,6 +71,9 @@ let ocamlexample_pwrite h buf offset _ > let offset = Int64.to_int offset in > String.blit buf 0 !disk offset len > > +let ocamlexample_thread_model () > + NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS > + > let plugin = { > NBDKit.default_callbacks with > (* name, open_connection, get_size and pread are required, > @@ -88,8 +91,8 @@ let plugin = { > get_size = Some ocamlexample_get_size; > pread = Some ocamlexample_pread; > pwrite = Some ocamlexample_pwrite; > + > + thread_model = Some ocamlexample_thread_model; > } > > -let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS > - > -let () = NBDKit.register_plugin thread_model plugin > +let () = NBDKit.register_plugin plugin > diff --git a/tests/test_ocaml_plugin.ml b/tests/test_ocaml_plugin.ml > index eb0d9319..3cf8fd90 100644 > --- a/tests/test_ocaml_plugin.ml > +++ b/tests/test_ocaml_plugin.ml > @@ -75,8 +75,7 @@ let plugin = { > pwrite = Some test_pwrite; > > extents = Some test_extents; > + thread_model = Some (fun () -> NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS); > } > > -let thread_model = NBDKit.THREAD_MODEL_SERIALIZE_CONNECTIONS > - > -let () = NBDKit.register_plugin thread_model plugin > +let () = NBDKit.register_plugin plugin > -- > 2.20.1 > > _______________________________________________ > Libguestfs mailing list > Libguestfs@redhat.com > https://www.redhat.com/mailman/listinfo/libguestfs-- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org
Eric Blake
2019-Aug-16 13:10 UTC
Re: [Libguestfs] [nbdkit PATCH] ocaml: Add support for dynamic .thread_model
On 8/15/19 4:52 PM, Eric Blake wrote:> We do not promise API stability for non-C languages; this is an API > break as follows: instead of calling 'NBDKit.register_plugin model > plugin' with a static model, you can now add .thread_model :(unit -> > thread_model) to plugin or default to PARALLEL. > > Since all existing OCaml plugins will have already thought about > thread models, they can convert their existing model into the new > plugin field (and thus, I don't feel too bad making PARALLEL the > default, even if it is not always the safest). > > Signed-off-by: Eric Blake <eblake@redhat.com> > --- > > I'm still looking at two followups: > 1) ./nbdkit doesn't set LD_LIBRARY_PATH=plugins/ocaml/.libs:$LD_LIBRARY_PATH > (making ./nbdkit --dump-plugin tests/test-ocaml-plugin.so fail to load > when the system nbdkit is too old) > 2) although --dump-plugin shows thread model, ./nbdkit -v log does not; > I need to add a debug() statement for that in server/locks.cDoing this proved I had a copy-paste bug:> +static int > +thread_model_wrapper (void) > +{ > + CAMLparam0 (); > + CAMLlocal1 (rv); > + > + caml_leave_blocking_section (); > + > + rv = caml_callback_exn (config_complete_fn, Val_unit);This needs to call thread_model_fn, not config_complete_fn; otherwise the thread model is wrongly chosen between 0 or 1, and in the --dump-plugin case I get an assertion in tests/test_ocaml_plugin.ml when not providing the expected config parameters. I've now pushed fixes for the two noted improvements, as well as this patch as fixed. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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