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sd-event: optionally, if an event source fails, exit the event loop

Browse Source 
Currently, if an event source callback returns an error, we'll disable
the event source and continue. This adds a per-event source flag that if
turned on goes further: the event loop is also exited, propagating the
error code.

This is inspired by some patterns repeatedly seen in #15206.

The idea is that event sources that server the "primary" function of a
program are marked like this, so that if they fail the failure is
instantly propagated and terminates the program.
This commit is contained in:
Lennart Poettering 2020-10-01 22:17:31 +02:00
parent ab582fda48
commit b778cba4bf
4 changed files with 48 additions and 8 deletions
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2
src/libsystemd/libsystemd.sym
View File

@ -726,6 +726,8 @@ LIBSYSTEMD_247 {
global:
sd_event_add_time_relative;
sd_event_source_set_time_relative;
sd_event_source_get_exit_on_failure;
sd_event_source_set_exit_on_failure;
sd_bus_error_has_names_sentinel;

1
src/libsystemd/sd-event/event-source.h
View File

@ -60,6 +60,7 @@ struct sd_event_source {
bool pending:1;
bool dispatching:1;
bool floating:1;
bool exit_on_failure:1;
int64_t priority;
unsigned pending_index;

51
src/libsystemd/sd-event/sd-event.c
View File

@ -3183,16 +3183,21 @@ static int process_inotify(sd_event *e) {
}
static int source_dispatch(sd_event_source *s) {
_cleanup_(sd_event_unrefp) sd_event *saved_event = NULL;
EventSourceType saved_type;
int r = 0;
assert(s);
assert(s->pending || s->type == SOURCE_EXIT);
/* Save the event source type, here, so that we still know it after the event callback which might invalidate
* the event. */
/* Save the event source type, here, so that we still know it after the event callback which might
* invalidate the event. */
saved_type = s->type;
/* Similar, store a reference to the event loop object, so that we can still access it after the
* callback might have invalidated/disconnected the event source. */
saved_event = sd_event_ref(s->event);
if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
r = source_set_pending(s, false);
if (r < 0)
@ -3299,9 +3304,15 @@ static int source_dispatch(sd_event_source *s) {
s->dispatching = false;
if (r < 0)
log_debug_errno(r, "Event source %s (type %s) returned error, disabling: %m",
strna(s->description), event_source_type_to_string(saved_type));
if (r < 0) {
log_debug_errno(r, "Event source %s (type %s) returned error, %s: %m",
strna(s->description),
event_source_type_to_string(saved_type),
s->exit_on_failure ? "exiting" : "disabling");
if (s->exit_on_failure)
(void) sd_event_exit(saved_event, r);
}
if (s->n_ref == 0)
source_free(s);
@ -3334,9 +3345,15 @@ static int event_prepare(sd_event *e) {
r = s->prepare(s, s->userdata);
s->dispatching = false;
if (r < 0)
log_debug_errno(r, "Prepare callback of event source %s (type %s) returned error, disabling: %m",
strna(s->description), event_source_type_to_string(s->type));
if (r < 0) {
log_debug_errno(r, "Prepare callback of event source %s (type %s) returned error, %s: %m",
strna(s->description),
event_source_type_to_string(s->type),
s->exit_on_failure ? "exiting" : "disabling");
if (s->exit_on_failure)
(void) sd_event_exit(e, r);
}
if (s->n_ref == 0)
source_free(s);
@ -3974,3 +3991,21 @@ _public_ int sd_event_source_set_floating(sd_event_source *s, int b) {
return 1;
}
_public_ int sd_event_source_get_exit_on_failure(sd_event_source *s) {
assert_return(s, -EINVAL);
assert_return(s->type != SOURCE_EXIT, -EDOM);
return s->exit_on_failure;
}
_public_ int sd_event_source_set_exit_on_failure(sd_event_source *s, int b) {
assert_return(s, -EINVAL);
assert_return(s->type != SOURCE_EXIT, -EDOM);
if (s->exit_on_failure == !!b)
return 0;
s->exit_on_failure = b;
return 1;
}

2
src/systemd/sd-event.h
View File

@ -160,6 +160,8 @@ int sd_event_source_set_destroy_callback(sd_event_source *s, sd_event_destroy_t
int sd_event_source_get_destroy_callback(sd_event_source *s, sd_event_destroy_t *ret);
int sd_event_source_get_floating(sd_event_source *s);
int sd_event_source_set_floating(sd_event_source *s, int b);
int sd_event_source_get_exit_on_failure(sd_event_source *s);
int sd_event_source_set_exit_on_failure(sd_event_source *s, int b);
/* Define helpers so that __attribute__((cleanup(sd_event_unrefp))) and similar may be used. */
_SD_DEFINE_POINTER_CLEANUP_FUNC(sd_event, sd_event_unref);