From a08c7d252f1489366ca8d370cebda93290f47ffe Mon Sep 17 00:00:00 2001 From: =?utf8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Wed, 6 Jun 2018 11:07:02 +0200 Subject: [PATCH] bus: optionally call a callbacks for cleanup This adds a function sd_bus_slot_set_destroy_callback() to set a function which can free userdata or perform other cleanups. sd_bus_slot_get_destory_callback() queries the callback, and is included for completeness. Without something like this, for floating asynchronous callbacks, which might be called or not, depending on the sequence of events, it's hard to perform resource cleanup. The alternative would be to always perform the cleanup from the caller too, but that requires more coordination and keeping of some shared state. It's nicer to keep the cleanup contained between the callback and the function that requests the callback. --- man/rules/meson.build | 4 ++ man/sd_bus_slot_set_destroy_callback.xml | 105 +++++++++++++++++++++++++++++++ src/libsystemd/libsystemd.sym | 6 ++ src/libsystemd/sd-bus/bus-internal.h | 1 + src/libsystemd/sd-bus/bus-slot.c | 20 ++++++ src/systemd/sd-bus.h | 3 + 6 files changed, 139 insertions(+) create mode 100644 man/sd_bus_slot_set_destroy_callback.xml diff --git a/man/rules/meson.build b/man/rules/meson.build index bfc267b..d354847 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -226,6 +226,10 @@ manpages = [ ['sd_bus_set_connected_signal', '3', ['sd_bus_get_connected_signal'], ''], ['sd_bus_set_sender', '3', ['sd_bus_get_sender'], ''], ['sd_bus_set_watch_bind', '3', ['sd_bus_get_watch_bind'], ''], + ['sd_bus_slot_set_destroy_callback', + '3', + ['sd_bus_slot_get_destroy_callback'], + ''], ['sd_bus_track_add_name', '3', ['sd_bus_track_add_sender', diff --git a/man/sd_bus_slot_set_destroy_callback.xml b/man/sd_bus_slot_set_destroy_callback.xml new file mode 100644 index 0000000..6334444 --- /dev/null +++ b/man/sd_bus_slot_set_destroy_callback.xml @@ -0,0 +1,105 @@ + + + + + + + + + sd_bus_slot_set_destroy_callback + systemd + + + + sd_bus_slot_set_destroy_callback + 3 + + + + sd_bus_slot_set_destroy_callback + sd_bus_slot_get_destroy_callback + + Define the callback function for resource cleanup. + + + + + #include <systemd/sd-bus.h> + + + typedef int (*sd_bus_destroy_t) + void *userdata + + + + int sd_bus_slot_set_destroy_callback + sd_bus_slot *slot + sd_bus_destroy_t callback + + + + int sd_bus_slot_get_destroy_callback + sd_bus_slot *slot + sd_bus_destroy_t *callback + + + + + + Description + + sd_bus_slot_set_destroy_callback() sets + callback as the callback function to be called right before the bus slot + object slot is deallocated. The userdata pointer + from the slot object will be passed as the userdata parameter. This + pointer can be set specified as an argument to the constuctor functions, see + sd_bus_add_match3, + or directly, see + sd_bus_set_userdata3. + This callback function is called even if userdata is + NULL. + + sd_bus_slot_get_destroy_callback() returns the current callback + for slot in the callback parameter. + + + + Return Value + + On success, sd_bus_slot_set_destroy_callback() returns 0 or a + positive integer. On failure, it returns a negative errno-style error code. + + sd_bus_slot_get_destroy_callback() returns 1 if the destroy callback + function is set, 0 if not. On failure, it returns a negative errno-style error code. + + + + Errors + + Returned errors may indicate the following problems: + + + + -EINVAL + + The slot parameter is NULL. + + + + + + + + + See Also + + + systemd1, + sd-bus3, + sd_bus_slot_set_floating3 + + + + diff --git a/src/libsystemd/libsystemd.sym b/src/libsystemd/libsystemd.sym index 00aeefb..49add9c 100644 --- a/src/libsystemd/libsystemd.sym +++ b/src/libsystemd/libsystemd.sym @@ -549,3 +549,9 @@ global: sd_event_source_get_io_fd_own; sd_event_source_set_io_fd_own; } LIBSYSTEMD_236; + +LIBSYSTEMD_239 { +global: + sd_bus_slot_get_destroy_callback; + sd_bus_slot_set_destroy_callback; +} LIBSYSTEMD_237; diff --git a/src/libsystemd/sd-bus/bus-internal.h b/src/libsystemd/sd-bus/bus-internal.h index 9c43771..721d6c7 100644 --- a/src/libsystemd/sd-bus/bus-internal.h +++ b/src/libsystemd/sd-bus/bus-internal.h @@ -142,6 +142,7 @@ struct sd_bus_slot { unsigned n_ref; sd_bus *bus; void *userdata; + sd_bus_destroy_t destroy_callback; BusSlotType type:5; bool floating:1; bool match_added:1; diff --git a/src/libsystemd/sd-bus/bus-slot.c b/src/libsystemd/sd-bus/bus-slot.c index 1e80f0c..7fd5368 100644 --- a/src/libsystemd/sd-bus/bus-slot.c +++ b/src/libsystemd/sd-bus/bus-slot.c @@ -217,6 +217,10 @@ _public_ sd_bus_slot* sd_bus_slot_unref(sd_bus_slot *slot) { } bus_slot_disconnect(slot); + + if (slot->destroy_callback) + slot->destroy_callback(slot->userdata); + free(slot->description); return mfree(slot); } @@ -244,6 +248,22 @@ _public_ void *sd_bus_slot_set_userdata(sd_bus_slot *slot, void *userdata) { return ret; } +_public_ int sd_bus_slot_set_destroy_callback(sd_bus_slot *slot, sd_bus_destroy_t callback) { + assert_return(slot, -EINVAL); + + slot->destroy_callback = callback; + return 0; +} + +_public_ int sd_bus_slot_get_destroy_callback(sd_bus_slot *slot, sd_bus_destroy_t *callback) { + assert_return(slot, -EINVAL); + + if (callback) + *callback = slot->destroy_callback; + + return !!slot->destroy_callback; +} + _public_ sd_bus_message *sd_bus_slot_get_current_message(sd_bus_slot *slot) { assert_return(slot, NULL); assert_return(slot->type >= 0, NULL); diff --git a/src/systemd/sd-bus.h b/src/systemd/sd-bus.h index 82e7d44..2db9c85 100644 --- a/src/systemd/sd-bus.h +++ b/src/systemd/sd-bus.h @@ -111,6 +111,7 @@ typedef int (*sd_bus_property_set_t) (sd_bus *bus, const char *path, const char typedef int (*sd_bus_object_find_t) (sd_bus *bus, const char *path, const char *interface, void *userdata, void **ret_found, sd_bus_error *ret_error); typedef int (*sd_bus_node_enumerator_t) (sd_bus *bus, const char *prefix, void *userdata, char ***ret_nodes, sd_bus_error *ret_error); typedef int (*sd_bus_track_handler_t) (sd_bus_track *track, void *userdata); +typedef void (*sd_bus_destroy_t)(void *userdata); #include "sd-bus-protocol.h" #include "sd-bus-vtable.h" @@ -222,6 +223,8 @@ void *sd_bus_slot_get_userdata(sd_bus_slot *slot); void *sd_bus_slot_set_userdata(sd_bus_slot *slot, void *userdata); int sd_bus_slot_set_description(sd_bus_slot *slot, const char *description); int sd_bus_slot_get_description(sd_bus_slot *slot, const char **description); +int sd_bus_slot_set_destroy_callback(sd_bus_slot *s, sd_bus_destroy_t callback); +int sd_bus_slot_get_destroy_callback(sd_bus_slot *s, sd_bus_destroy_t *callback); sd_bus_message* sd_bus_slot_get_current_message(sd_bus_slot *slot); sd_bus_message_handler_t sd_bus_slot_get_current_handler(sd_bus_slot *bus); -- 2.7.4