* The application's registration hooks should be called ONLY via
* these macros, with the ctx locked. Likewise all the "occurred"
* entrypoints from the application should assert(!in_hook);
+ *
+ * During the hook call - including while the arguments are being
+ * evaluated - ev->nexus is guaranteed to be valid and refer to the
+ * nexus which is being used for this event registration. The
+ * arguments should specify ev->nexus for the for_libxl argument and
+ * ev->nexus->for_app_reg (or a pointer to it) for for_app_reg.
*/
-#define OSEVENT_HOOK_INTERN(retval, hookname, ...) do { \
- if (CTX->osevent_hooks) { \
- CTX->osevent_in_hook++; \
- retval CTX->osevent_hooks->hookname(CTX->osevent_user, __VA_ARGS__); \
- CTX->osevent_in_hook--; \
- } \
+#define OSEVENT_HOOK_INTERN(retval, failedp, evkind, hookop, nexusop, ...) do { \
+ if (CTX->osevent_hooks) { \
+ CTX->osevent_in_hook++; \
+ libxl__osevent_hook_nexi *nexi = &CTX->hook_##evkind##_nexi_idle; \
+ osevent_hook_pre_##nexusop(gc, ev, nexi, &ev->nexus); \
+ retval CTX->osevent_hooks->evkind##_##hookop \
+ (CTX->osevent_user, __VA_ARGS__); \
+ if ((failedp)) \
+ osevent_hook_failed_##nexusop(gc, ev, nexi, &ev->nexus); \
+ CTX->osevent_in_hook--; \
+ } \
} while (0)
-#define OSEVENT_HOOK(hookname, ...) ({ \
- int osevent_hook_rc = 0; \
- OSEVENT_HOOK_INTERN(osevent_hook_rc = , hookname, __VA_ARGS__); \
- osevent_hook_rc; \
+#define OSEVENT_HOOK(evkind, hookop, nexusop, ...) ({ \
+ int osevent_hook_rc = 0; \
+ OSEVENT_HOOK_INTERN(osevent_hook_rc =, !!osevent_hook_rc, \
+ evkind, hookop, nexusop, __VA_ARGS__); \
+ osevent_hook_rc; \
})
-#define OSEVENT_HOOK_VOID(hookname, ...) \
- OSEVENT_HOOK_INTERN(/* void */, hookname, __VA_ARGS__)
+#define OSEVENT_HOOK_VOID(evkind, hookop, nexusop, ...) \
+ OSEVENT_HOOK_INTERN(/* void */, 0, evkind, hookop, nexusop, __VA_ARGS__)
+
+/*
+ * The application's calls to libxl_osevent_occurred_... may be
+ * indefinitely delayed with respect to the rest of the program (since
+ * they are not necessarily called with any lock held). So the
+ * for_libxl value we receive may be (almost) arbitrarily old. All we
+ * know is that it came from this ctx.
+ *
+ * Therefore we may not free the object referred to by any for_libxl
+ * value until we free the whole libxl_ctx. And if we reuse it we
+ * must be able to tell when an old use turns up, and discard the
+ * stale event.
+ *
+ * Thus we cannot use the ev directly as the for_libxl value - we need
+ * a layer of indirection.
+ *
+ * We do this by keeping a pool of libxl__osevent_hook_nexus structs,
+ * and use pointers to them as for_libxl values. In fact, there are
+ * two pools: one for fds and one for timeouts. This ensures that we
+ * don't risk a type error when we upcast nexus->ev. In each nexus
+ * the ev is either null or points to a valid libxl__ev_time or
+ * libxl__ev_fd, as applicable.
+ *
+ * We /do/ allow ourselves to reassociate an old nexus with a new ev
+ * as otherwise we would have to leak nexi. (This reassociation
+ * might, of course, be an old ev being reused for a new purpose so
+ * simply comparing the ev pointer is not sufficient.) Thus the
+ * libxl_osevent_occurred functions need to check that the condition
+ * allegedly signalled by this event actually exists.
+ *
+ * The nexi and the lists are all protected by the ctx lock.
+ */
+
+struct libxl__osevent_hook_nexus {
+ void *ev;
+ void *for_app_reg;
+ LIBXL_SLIST_ENTRY(libxl__osevent_hook_nexus) next;
+};
+
+static void *osevent_ev_from_hook_nexus(libxl_ctx *ctx,
+ libxl__osevent_hook_nexus *nexus /* pass void *for_libxl */)
+{
+ return nexus->ev;
+}
+
+static void osevent_release_nexus(libxl__gc *gc,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus *nexus)
+{
+ nexus->ev = 0;
+ LIBXL_SLIST_INSERT_HEAD(nexi_idle, nexus, next);
+}
+
+/*----- OSEVENT* hook functions for nexusop "alloc" -----*/
+static void osevent_hook_pre_alloc(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus_r)
+{
+ libxl__osevent_hook_nexus *nexus = LIBXL_SLIST_FIRST(nexi_idle);
+ if (nexus) {
+ LIBXL_SLIST_REMOVE_HEAD(nexi_idle, next);
+ } else {
+ nexus = libxl__zalloc(NOGC, sizeof(*nexus));
+ }
+ nexus->ev = ev;
+ *nexus_r = nexus;
+}
+static void osevent_hook_failed_alloc(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus)
+{
+ osevent_release_nexus(gc, nexi_idle, *nexus);
+}
+
+/*----- OSEVENT* hook functions for nexusop "release" -----*/
+static void osevent_hook_pre_release(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus)
+{
+ osevent_release_nexus(gc, nexi_idle, *nexus);
+}
+static void osevent_hook_failed_release(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus)
+{
+ abort();
+}
+
+/*----- OSEVENT* hook functions for nexusop "noop" -----*/
+static void osevent_hook_pre_noop(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus) { }
+static void osevent_hook_failed_noop(libxl__gc *gc, void *ev,
+ libxl__osevent_hook_nexi *nexi_idle,
+ libxl__osevent_hook_nexus **nexus) { }
+
/*
* fd events
DBG("ev_fd=%p register fd=%d events=%x", ev, fd, events);
- rc = OSEVENT_HOOK(fd_register, fd, &ev->for_app_reg, events, ev);
+ rc = OSEVENT_HOOK(fd,register, alloc, fd, &ev->nexus->for_app_reg,
+ events, ev->nexus);
if (rc) goto out;
ev->fd = fd;
DBG("ev_fd=%p modify fd=%d events=%x", ev, ev->fd, events);
- rc = OSEVENT_HOOK(fd_modify, ev->fd, &ev->for_app_reg, events);
+ rc = OSEVENT_HOOK(fd,modify, noop, ev->fd, &ev->nexus->for_app_reg, events);
if (rc) goto out;
ev->events = events;
DBG("ev_fd=%p deregister fd=%d", ev, ev->fd);
- OSEVENT_HOOK_VOID(fd_deregister, ev->fd, ev->for_app_reg);
+ OSEVENT_HOOK_VOID(fd,deregister, release, ev->fd, ev->nexus->for_app_reg);
LIBXL_LIST_REMOVE(ev, entry);
ev->fd = -1;
{
int rc;
- rc = OSEVENT_HOOK(timeout_register, &ev->for_app_reg, absolute, ev);
+ rc = OSEVENT_HOOK(timeout,register, alloc, &ev->nexus->for_app_reg,
+ absolute, ev->nexus);
if (rc) return rc;
ev->infinite = 0;
static void time_deregister(libxl__gc *gc, libxl__ev_time *ev)
{
if (!ev->infinite) {
- OSEVENT_HOOK_VOID(timeout_deregister, ev->for_app_reg);
+ OSEVENT_HOOK_VOID(timeout,deregister, release, ev->nexus->for_app_reg);
LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
}
}
rc = time_register_finite(gc, ev, absolute);
if (rc) goto out;
} else {
- rc = OSEVENT_HOOK(timeout_modify, &ev->for_app_reg, absolute);
+ rc = OSEVENT_HOOK(timeout,modify, noop,
+ &ev->nexus->for_app_reg, absolute);
if (rc) goto out;
LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
void libxl_osevent_occurred_fd(libxl_ctx *ctx, void *for_libxl,
- int fd, short events, short revents)
+ int fd, short events_ign, short revents_ign)
{
- libxl__ev_fd *ev = for_libxl;
-
EGC_INIT(ctx);
CTX_LOCK;
assert(!CTX->osevent_in_hook);
- assert(fd == ev->fd);
- revents &= ev->events;
- if (revents)
- ev->func(egc, ev, fd, ev->events, revents);
+ libxl__ev_fd *ev = osevent_ev_from_hook_nexus(ctx, for_libxl);
+ if (!ev) goto out;
+ if (ev->fd != fd) goto out;
+ struct pollfd check;
+ for (;;) {
+ check.fd = fd;
+ check.events = ev->events;
+ int r = poll(&check, 1, 0);
+ if (!r)
+ goto out;
+ if (r==1)
+ break;
+ assert(r<0);
+ if (errno != EINTR) {
+ LIBXL__EVENT_DISASTER(egc, "failed poll to check for fd", errno, 0);
+ goto out;
+ }
+ }
+
+ if (check.revents)
+ ev->func(egc, ev, fd, ev->events, check.revents);
+
+ out:
CTX_UNLOCK;
EGC_FREE;
}
void libxl_osevent_occurred_timeout(libxl_ctx *ctx, void *for_libxl)
{
- libxl__ev_time *ev = for_libxl;
-
EGC_INIT(ctx);
CTX_LOCK;
assert(!CTX->osevent_in_hook);
+ libxl__ev_time *ev = osevent_ev_from_hook_nexus(ctx, for_libxl);
+ if (!ev) goto out;
assert(!ev->infinite);
+
LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
ev->func(egc, ev, &ev->abs);
+ out:
CTX_UNLOCK;
EGC_FREE;
}
projects / xen.git / commitdiff