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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 3/3] libxl: ocaml: use 'for_app_registration' in osevent callbacks
This allows the application to pass a token to libxl in the fd/timeout
registration callbacks, which it receives back in modification or
deregistration callbacks.
It turns out that this is essential for timeout handling, in order to
identify which timeout to change on a modify event.
Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
Acked-by: David Scott <dave.scott@xxxxxxxxxxxxx>
---
v2:
* assert if for_app == NULL
* catch any exceptions from callbacks
* use goto-style error handling ;)
v3:
* for timeouts, cleanup for_app in occurred_timeout (not in
timeout_deregister)
* improve comments
* abort in fd_deregister when the app raises an exception
v4:
* made for_app a value inside the handles struct, rather than a value*
* ensure handles are cleaned up in the error path
* rename timeout_modify to timeout_fire_now on the ocaml side
---
tools/ocaml/libs/xl/xenlight.ml.in | 4 +-
tools/ocaml/libs/xl/xenlight.mli.in | 10 +--
tools/ocaml/libs/xl/xenlight_stubs.c | 147 +++++++++++++++++++++++++++++-----
3 files changed, 135 insertions(+), 26 deletions(-)
diff --git a/tools/ocaml/libs/xl/xenlight.ml.in
b/tools/ocaml/libs/xl/xenlight.ml.in
index 47f3487..80e620a 100644
--- a/tools/ocaml/libs/xl/xenlight.ml.in
+++ b/tools/ocaml/libs/xl/xenlight.ml.in
@@ -68,12 +68,12 @@ module Async = struct
external osevent_occurred_fd : ctx -> for_libxl -> Unix.file_descr ->
event list -> event list -> unit = "stub_libxl_osevent_occurred_fd"
external osevent_occurred_timeout : ctx -> for_libxl -> unit =
"stub_libxl_osevent_occurred_timeout"
- let osevent_register_hooks ctx ~user ~fd_register ~fd_modify
~fd_deregister ~timeout_register ~timeout_modify =
+ let osevent_register_hooks ctx ~user ~fd_register ~fd_modify
~fd_deregister ~timeout_register ~timeout_fire_now =
Callback.register "libxl_fd_register" fd_register;
Callback.register "libxl_fd_modify" fd_modify;
Callback.register "libxl_fd_deregister" fd_deregister;
Callback.register "libxl_timeout_register" timeout_register;
- Callback.register "libxl_timeout_modify" timeout_modify;
+ Callback.register "libxl_timeout_fire_now" timeout_fire_now;
osevent_register_hooks' ctx user
let async_register_callback ~async_callback =
diff --git a/tools/ocaml/libs/xl/xenlight.mli.in
b/tools/ocaml/libs/xl/xenlight.mli.in
index b9819e1..b2c06b5 100644
--- a/tools/ocaml/libs/xl/xenlight.mli.in
+++ b/tools/ocaml/libs/xl/xenlight.mli.in
@@ -68,11 +68,11 @@ module Async : sig
val osevent_register_hooks : ctx ->
user:'a ->
- fd_register:('a -> Unix.file_descr -> event list -> for_libxl
-> unit) ->
- fd_modify:('a -> Unix.file_descr -> event list -> unit) ->
- fd_deregister:('a -> Unix.file_descr -> unit) ->
- timeout_register:('a -> int64 -> int64 -> for_libxl -> unit) ->
- timeout_modify:('a -> unit) ->
+ fd_register:('a -> Unix.file_descr -> event list -> for_libxl
-> 'b) ->
+ fd_modify:('a -> Unix.file_descr -> 'b -> event list -> 'b) ->
+ fd_deregister:('a -> Unix.file_descr -> 'b -> unit) ->
+ timeout_register:('a -> int64 -> int64 -> for_libxl -> 'c) ->
+ timeout_fire_now:('a -> 'c -> 'c) ->
osevent_hooks
external osevent_occurred_fd : ctx -> for_libxl -> Unix.file_descr ->
event list -> event list -> unit = "stub_libxl_osevent_occurred_fd"
diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c
b/tools/ocaml/libs/xl/xenlight_stubs.c
index 2e2606a..21fbe00 100644
--- a/tools/ocaml/libs/xl/xenlight_stubs.c
+++ b/tools/ocaml/libs/xl/xenlight_stubs.c
@@ -31,6 +31,7 @@
#include <libxl_utils.h>
#include <unistd.h>
+#include <assert.h>
#include "caml_xentoollog.h"
@@ -1211,14 +1212,20 @@ value Val_poll_events(short events)
CAMLreturn(event_list);
}
+/* The process for dealing with the for_app_registration_ values in the
+ * callbacks below (GC registrations etc) is similar to the way for_callback is
+ * handled in the asynchronous operations above. */
+
int fd_register(void *user, int fd, void **for_app_registration_out,
short events, void *for_libxl)
{
caml_leave_blocking_section();
CAMLparam0();
CAMLlocalN(args, 4);
+ int ret = 0;
static value *func = NULL;
value *p = (value *) user;
+ value *for_app;
if (func == NULL) {
/* First time around, lookup by name */
@@ -1230,10 +1237,25 @@ int fd_register(void *user, int fd, void
**for_app_registration_out,
args[2] = Val_poll_events(events);
args[3] = (value) for_libxl;
- caml_callbackN(*func, 4, args);
+ for_app = malloc(sizeof(value));
+ if (!for_app) {
+ ret = ERROR_OSEVENT_REG_FAIL;
+ goto err;
+ }
+
+ *for_app = caml_callbackN_exn(*func, 4, args);
+ if (Is_exception_result(*for_app)) {
+ ret = ERROR_OSEVENT_REG_FAIL;
+ goto err;
+ }
+
+ caml_register_global_root(for_app);
+ *for_app_registration_out = for_app;
+
+err:
CAMLdone;
caml_enter_blocking_section();
- return 0;
+ return ret;
}
int fd_modify(void *user, int fd, void **for_app_registration_update,
@@ -1241,9 +1263,14 @@ int fd_modify(void *user, int fd, void
**for_app_registration_update,
{
caml_leave_blocking_section();
CAMLparam0();
- CAMLlocalN(args, 3);
+ CAMLlocalN(args, 4);
+ int ret = 0;
static value *func = NULL;
value *p = (value *) user;
+ value *for_app = *for_app_registration_update;
+
+ /* If for_app == NULL, then something is very wrong */
+ assert(for_app);
if (func == NULL) {
/* First time around, lookup by name */
@@ -1252,21 +1279,37 @@ int fd_modify(void *user, int fd, void
**for_app_registration_update,
args[0] = *p;
args[1] = Val_int(fd);
- args[2] = Val_poll_events(events);
+ args[2] = *for_app;
+ args[3] = Val_poll_events(events);
+
+ *for_app = caml_callbackN_exn(*func, 4, args);
+ if (Is_exception_result(*for_app)) {
+ /* If an exception is caught, *for_app_registration_update is
not
+ * changed. It remains a valid pointer to a value that is
registered
+ * with the GC. */
+ ret = ERROR_OSEVENT_REG_FAIL;
+ goto err;
+ }
+
+ *for_app_registration_update = for_app;
- caml_callbackN(*func, 3, args);
+err:
CAMLdone;
caml_enter_blocking_section();
- return 0;
+ return ret;
}
void fd_deregister(void *user, int fd, void *for_app_registration)
{
caml_leave_blocking_section();
CAMLparam0();
- CAMLlocalN(args, 2);
+ CAMLlocalN(args, 3);
static value *func = NULL;
value *p = (value *) user;
+ value *for_app = for_app_registration;
+
+ /* If for_app == NULL, then something is very wrong */
+ assert(for_app);
if (func == NULL) {
/* First time around, lookup by name */
@@ -1275,12 +1318,26 @@ void fd_deregister(void *user, int fd, void
*for_app_registration)
args[0] = *p;
args[1] = Val_int(fd);
+ args[2] = *for_app;
+
+ caml_callbackN_exn(*func, 3, args);
+ /* This hook does not return error codes, so the best thing we can do
+ * to avoid trouble, if we catch an exception from the app, is abort. */
+ if (Is_exception_result(*for_app))
+ abort();
+
+ caml_remove_global_root(for_app);
+ free(for_app);
- caml_callbackN(*func, 2, args);
CAMLdone;
caml_enter_blocking_section();
}
+struct timeout_handles {
+ void *for_libxl;
+ value for_app;
+};
+
int timeout_register(void *user, void **for_app_registration_out,
struct timeval abs, void *for_libxl)
{
@@ -1288,8 +1345,10 @@ int timeout_register(void *user, void
**for_app_registration_out,
CAMLparam0();
CAMLlocal2(sec, usec);
CAMLlocalN(args, 4);
+ int ret = 0;
static value *func = NULL;
value *p = (value *) user;
+ struct timeout_handles *handles;
if (func == NULL) {
/* First time around, lookup by name */
@@ -1299,15 +1358,37 @@ int timeout_register(void *user, void
**for_app_registration_out,
sec = caml_copy_int64(abs.tv_sec);
usec = caml_copy_int64(abs.tv_usec);
+ /* This struct of "handles" will contain "for_libxl" as well as
"for_app".
+ * We'll give a pointer to the struct to the app, and get it back in
+ * occurred_timeout, where we can clean it all up. */
+ handles = malloc(sizeof(*handles));
+ if (!handles) {
+ ret = ERROR_OSEVENT_REG_FAIL;
+ goto err;
+ }
+
+ handles->for_libxl = for_libxl;
+
args[0] = *p;
args[1] = sec;
args[2] = usec;
- args[3] = (value) for_libxl;
+ args[3] = (value) handles;
+
+ handles->for_app = caml_callbackN_exn(*func, 4, args);
+ if (Is_exception_result(handles->for_app)) {
+ ret = ERROR_OSEVENT_REG_FAIL;
+ caml_remove_global_root(&handles->for_app);
+ free(handles);
+ goto err;
+ }
- caml_callbackN(*func, 4, args);
+ caml_register_global_root(&handles->for_app);
+ *for_app_registration_out = handles;
+
+err:
CAMLdone;
caml_enter_blocking_section();
- return 0;
+ return ret;
}
int timeout_modify(void *user, void **for_app_registration_update,
@@ -1315,25 +1396,49 @@ int timeout_modify(void *user, void
**for_app_registration_update,
{
caml_leave_blocking_section();
CAMLparam0();
+ CAMLlocal1(for_app_update);
+ CAMLlocalN(args, 2);
+ int ret = 0;
static value *func = NULL;
value *p = (value *) user;
+ struct timeout_handles *handles = *for_app_registration_update;
+
+ /* If for_app == NULL, then something is very wrong */
+ assert(handles->for_app);
+
+ /* Libxl currently promises that timeout_modify is only ever called with
+ * abs={0,0}, meaning "right away". We cannot deal with other values. */
+ assert(abs.tv_sec == 0 && abs.tv_usec == 0);
if (func == NULL) {
/* First time around, lookup by name */
- func = caml_named_value("libxl_timeout_modify");
+ func = caml_named_value("libxl_timeout_fire_now");
}
- caml_callback(*func, *p);
+ args[0] = *p;
+ args[1] = handles->for_app;
+
+ for_app_update = caml_callbackN_exn(*func, 2, args);
+ if (Is_exception_result(for_app_update)) {
+ /* If an exception is caught, *for_app_registration_update is
not
+ * changed. It remains a valid pointer to a value that is
registered
+ * with the GC. */
+ ret = ERROR_OSEVENT_REG_FAIL;
+ goto err;
+ }
+
+ handles->for_app = for_app_update;
+
+err:
CAMLdone;
caml_enter_blocking_section();
- return 0;
+ return ret;
}
void timeout_deregister(void *user, void *for_app_registration)
{
- caml_leave_blocking_section();
- failwith_xl(ERROR_FAIL, "timeout_deregister not yet implemented");
- caml_enter_blocking_section();
+ /* This hook will never be called by libxl. */
+ abort();
}
value stub_libxl_osevent_register_hooks(value ctx, value user)
@@ -1386,12 +1491,16 @@ value stub_libxl_osevent_occurred_fd(value ctx, value
for_libxl, value fd,
value stub_libxl_osevent_occurred_timeout(value ctx, value for_libxl)
{
- CAMLparam2(ctx, for_libxl);
+ CAMLparam1(ctx);
+ struct timeout_handles *handles = (struct timeout_handles *) for_libxl;
caml_enter_blocking_section();
- libxl_osevent_occurred_timeout(CTX, (void *) for_libxl);
+ libxl_osevent_occurred_timeout(CTX, (void *) handles->for_libxl);
caml_leave_blocking_section();
+ caml_remove_global_root(&handles->for_app);
+ free(handles);
+
CAMLreturn(Val_unit);
}
--
1.7.10.4
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