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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 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>
---
v2:
* assert if for_app == NULL
* catch any exceptions from callbacks
* use goto-style error handling ;)
---
tools/ocaml/libs/xl/xenlight.mli.in | 10 +--
tools/ocaml/libs/xl/xenlight_stubs.c | 116 ++++++++++++++++++++++++++++++----
2 files changed, 109 insertions(+), 17 deletions(-)
diff --git a/tools/ocaml/libs/xl/xenlight.mli.in
b/tools/ocaml/libs/xl/xenlight.mli.in
index b9819e1..277e81d 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_modify:('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..997cbe6 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, assume that something is 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, assume that something is wrong */
+ assert(for_app);
if (func == NULL) {
/* First time around, lookup by name */
@@ -1275,8 +1318,15 @@ 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);
+ /* If the callback were to raise an exception, this will be ignored;
+ * this hook does not return error codes */
+
+ caml_remove_global_root(for_app);
+ free(for_app);
- caml_callbackN(*func, 2, args);
CAMLdone;
caml_enter_blocking_section();
}
@@ -1288,8 +1338,10 @@ 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;
+ value *for_app;
if (func == NULL) {
/* First time around, lookup by name */
@@ -1304,10 +1356,25 @@ int timeout_register(void *user, void
**for_app_registration_out,
args[2] = usec;
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 timeout_modify(void *user, void **for_app_registration_update,
@@ -1315,18 +1382,43 @@ int timeout_modify(void *user, void
**for_app_registration_update,
{
caml_leave_blocking_section();
CAMLparam0();
+ CAMLlocalN(args, 2);
+ int ret = 0;
static value *func = NULL;
value *p = (value *) user;
+ value *for_app = *for_app_registration_update;
+
+ /* If for_app == NULL, assume that something is wrong */
+ assert(for_app);
if (func == NULL) {
/* First time around, lookup by name */
func = caml_named_value("libxl_timeout_modify");
}
- caml_callback(*func, *p);
+ args[0] = *p;
+ args[1] = *for_app;
+
+ *for_app = caml_callbackN_exn(*func, 2, 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;
+ }
+
+ /* This modify hook causes the timeout to fire immediately. Deregister
+ * won't be called, so we clean up our GC registration here. */
+ caml_remove_global_root(for_app);
+ free(for_app);
+ *for_app_registration_update = NULL;
+
+err:
CAMLdone;
caml_enter_blocking_section();
- return 0;
+ return ret;
}
void timeout_deregister(void *user, void *for_app_registration)
--
1.7.10.4
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