sd-event: introduce concept of "floating" event sources

These are the counterpart of "floating" bus slots, i.e. event sources
that are bound to the lifetime of the event object itself, and thus
don't require an explicit reference to be kept.

1 files changed, 126 insertions, 80 deletions

diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index 47970879da..06af962dfb 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -33,6 +33,7 @@
 #include "time-util.h"
 #include "missing.h"
 #include "set.h"
+#include "list.h"
 
 #include "sd-event.h"
 
@@ -51,7 +52,7 @@ typedef enum EventSourceType {
         SOURCE_POST,
         SOURCE_EXIT,
         SOURCE_WATCHDOG,
-        _SOUFCE_EVENT_SOURCE_TYPE_MAX,
+        _SOURCE_EVENT_SOURCE_TYPE_MAX,
         _SOURCE_EVENT_SOURCE_TYPE_INVALID = -1
 } EventSourceType;
 
@@ -68,6 +69,7 @@ struct sd_event_source {
         int enabled:3;
         bool pending:1;
         bool dispatching:1;
+        bool floating:1;
 
         int64_t priority;
         unsigned pending_index;
@@ -75,6 +77,8 @@ struct sd_event_source {
         unsigned pending_iteration;
         unsigned prepare_iteration;
 
+        LIST_FIELDS(sd_event_source, sources);
+
         union {
                 struct {
                         sd_event_io_handler_t callback;
@@ -177,8 +181,12 @@ struct sd_event {
         usec_t watchdog_last, watchdog_period;
 
         unsigned n_sources;
+
+        LIST_HEAD(sd_event_source, sources);
 };
 
+static void source_disconnect(sd_event_source *s);
+
 static int pending_prioq_compare(const void *a, const void *b) {
         const sd_event_source *x = a, *y = b;
 
@@ -349,7 +357,16 @@ static void free_clock_data(struct clock_data *d) {
 }
 
 static void event_free(sd_event *e) {
+        sd_event_source *s;
+
         assert(e);
+
+        while ((s = e->sources)) {
+                assert(s->floating);
+                source_disconnect(s);
+                sd_event_source_unref(s);
+        }
+
         assert(e->n_sources == 0);
 
         if (e->default_event_ptr)
@@ -557,86 +574,101 @@ static struct clock_data* event_get_clock_data(sd_event *e, EventSourceType t) {
         }
 }
 
-static void source_free(sd_event_source *s) {
+static void source_disconnect(sd_event_source *s) {
+        sd_event *event;
+
         assert(s);
 
-        if (s->event) {
-                assert(s->event->n_sources > 0);
+        if (!s->event)
+                return;
 
-                switch (s->type) {
+        assert(s->event->n_sources > 0);
 
-                case SOURCE_IO:
-                        if (s->io.fd >= 0)
-                                source_io_unregister(s);
+        switch (s->type) {
 
-                        break;
+        case SOURCE_IO:
+                if (s->io.fd >= 0)
+                        source_io_unregister(s);
 
-                case SOURCE_TIME_REALTIME:
-                case SOURCE_TIME_MONOTONIC:
-                case SOURCE_TIME_REALTIME_ALARM:
-                case SOURCE_TIME_BOOTTIME_ALARM: {
-                        struct clock_data *d;
+                break;
 
-                        d = event_get_clock_data(s->event, s->type);
-                        assert(d);
+        case SOURCE_TIME_REALTIME:
+        case SOURCE_TIME_MONOTONIC:
+        case SOURCE_TIME_REALTIME_ALARM:
+        case SOURCE_TIME_BOOTTIME_ALARM: {
+                struct clock_data *d;
 
-                        prioq_remove(d->earliest, s, &s->time.earliest_index);
-                        prioq_remove(d->latest, s, &s->time.latest_index);
-                        break;
+                d = event_get_clock_data(s->event, s->type);
+                assert(d);
+
+                prioq_remove(d->earliest, s, &s->time.earliest_index);
+                prioq_remove(d->latest, s, &s->time.latest_index);
+                break;
+        }
+
+        case SOURCE_SIGNAL:
+                if (s->signal.sig > 0) {
+                        if (s->signal.sig != SIGCHLD || s->event->n_enabled_child_sources == 0)
+                                assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);
+
+                        if (s->event->signal_sources)
+                                s->event->signal_sources[s->signal.sig] = NULL;
                 }
 
-                case SOURCE_SIGNAL:
-                        if (s->signal.sig > 0) {
-                                if (s->signal.sig != SIGCHLD || s->event->n_enabled_child_sources == 0)
-                                        assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);
+                break;
 
-                                if (s->event->signal_sources)
-                                        s->event->signal_sources[s->signal.sig] = NULL;
+        case SOURCE_CHILD:
+                if (s->child.pid > 0) {
+                        if (s->enabled != SD_EVENT_OFF) {
+                                assert(s->event->n_enabled_child_sources > 0);
+                                s->event->n_enabled_child_sources--;
                         }
 
-                        break;
+                        if (!s->event->signal_sources || !s->event->signal_sources[SIGCHLD])
+                                assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);
 
-                case SOURCE_CHILD:
-                        if (s->child.pid > 0) {
-                                if (s->enabled != SD_EVENT_OFF) {
-                                        assert(s->event->n_enabled_child_sources > 0);
-                                        s->event->n_enabled_child_sources--;
-                                }
+                        hashmap_remove(s->event->child_sources, INT_TO_PTR(s->child.pid));
+                }
 
-                                if (!s->event->signal_sources || !s->event->signal_sources[SIGCHLD])
-                                        assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);
+                break;
 
-                                hashmap_remove(s->event->child_sources, INT_TO_PTR(s->child.pid));
-                        }
+        case SOURCE_DEFER:
+                /* nothing */
+                break;
 
-                        break;
+        case SOURCE_POST:
+                set_remove(s->event->post_sources, s);
+                break;
 
-                case SOURCE_DEFER:
-                        /* nothing */
-                        break;
+        case SOURCE_EXIT:
+                prioq_remove(s->event->exit, s, &s->exit.prioq_index);
+                break;
 
-                case SOURCE_POST:
-                        set_remove(s->event->post_sources, s);
-                        break;
+        default:
+                assert_not_reached("Wut? I shouldn't exist.");
+        }
 
-                case SOURCE_EXIT:
-                        prioq_remove(s->event->exit, s, &s->exit.prioq_index);
-                        break;
+        if (s->pending)
+                prioq_remove(s->event->pending, s, &s->pending_index);
 
-                default:
-                        assert_not_reached("Wut? I shouldn't exist.");
-                }
+        if (s->prepare)
+                prioq_remove(s->event->prepare, s, &s->prepare_index);
 
-                if (s->pending)
-                        prioq_remove(s->event->pending, s, &s->pending_index);
+        event = s->event;
 
-                if (s->prepare)
-                        prioq_remove(s->event->prepare, s, &s->prepare_index);
+        s->type = _SOURCE_EVENT_SOURCE_TYPE_INVALID;
+        s->event = NULL;
+        LIST_REMOVE(sources, event->sources, s);
+        event->n_sources--;
 
-                s->event->n_sources--;
-                sd_event_unref(s->event);
-        }
+        if (!s->floating)
+                sd_event_unref(event);
+}
+
+static void source_free(sd_event_source *s) {
+        assert(s);
 
+        source_disconnect(s);
         free(s);
 }
 
@@ -675,7 +707,7 @@ static int source_set_pending(sd_event_source *s, bool b) {
         return 0;
 }
 
-static sd_event_source *source_new(sd_event *e, EventSourceType type) {
+static sd_event_source *source_new(sd_event *e, bool floating, EventSourceType type) {
         sd_event_source *s;
 
         assert(e);
@@ -685,10 +717,15 @@ static sd_event_source *source_new(sd_event *e, EventSourceType type) {
                 return NULL;
 
         s->n_ref = 1;
-        s->event = sd_event_ref(e);
+        s->event = e;
         s->type = type;
         s->pending_index = s->prepare_index = PRIOQ_IDX_NULL;
+        s->floating = floating;
+
+        if (!floating)
+                sd_event_ref(e);
 
+        LIST_PREPEND(sources, e->sources, s);
         e->n_sources ++;
 
         return s;
@@ -709,11 +746,10 @@ _public_ int sd_event_add_io(
         assert_return(fd >= 0, -EINVAL);
         assert_return(!(events & ~(EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET)), -EINVAL);
         assert_return(callback, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        s = source_new(e, SOURCE_IO);
+        s = source_new(e, !ret, SOURCE_IO);
         if (!s)
                 return -ENOMEM;
 
@@ -729,7 +765,9 @@ _public_ int sd_event_add_io(
                 return -errno;
         }
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -798,7 +836,6 @@ _public_ int sd_event_add_time(
         int r;
 
         assert_return(e, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(usec != (uint64_t) -1, -EINVAL);
         assert_return(accuracy != (uint64_t) -1, -EINVAL);
         assert_return(callback, -EINVAL);
@@ -829,7 +866,7 @@ _public_ int sd_event_add_time(
                         return r;
         }
 
-        s = source_new(e, type);
+        s = source_new(e, !ret, type);
         if (!s)
                 return -ENOMEM;
 
@@ -848,7 +885,9 @@ _public_ int sd_event_add_time(
         if (r < 0)
                 goto fail;
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 
 fail:
@@ -906,7 +945,6 @@ _public_ int sd_event_add_signal(
         assert_return(e, -EINVAL);
         assert_return(sig > 0, -EINVAL);
         assert_return(sig < _NSIG, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -927,7 +965,7 @@ _public_ int sd_event_add_signal(
         } else if (e->signal_sources[sig])
                 return -EBUSY;
 
-        s = source_new(e, SOURCE_SIGNAL);
+        s = source_new(e, !ret, SOURCE_SIGNAL);
         if (!s)
                 return -ENOMEM;
 
@@ -947,7 +985,9 @@ _public_ int sd_event_add_signal(
                 }
         }
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -967,7 +1007,6 @@ _public_ int sd_event_add_child(
         assert_return(!(options & ~(WEXITED|WSTOPPED|WCONTINUED)), -EINVAL);
         assert_return(options != 0, -EINVAL);
         assert_return(callback, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -978,7 +1017,7 @@ _public_ int sd_event_add_child(
         if (hashmap_contains(e->child_sources, INT_TO_PTR(pid)))
                 return -EBUSY;
 
-        s = source_new(e, SOURCE_CHILD);
+        s = source_new(e, !ret, SOURCE_CHILD);
         if (!s)
                 return -ENOMEM;
 
@@ -1008,7 +1047,9 @@ _public_ int sd_event_add_child(
 
         e->need_process_child = true;
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -1023,11 +1064,10 @@ _public_ int sd_event_add_defer(
 
         assert_return(e, -EINVAL);
         assert_return(callback, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        s = source_new(e, SOURCE_DEFER);
+        s = source_new(e, !ret, SOURCE_DEFER);
         if (!s)
                 return -ENOMEM;
 
@@ -1041,7 +1081,9 @@ _public_ int sd_event_add_defer(
                 return r;
         }
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -1056,7 +1098,6 @@ _public_ int sd_event_add_post(
 
         assert_return(e, -EINVAL);
         assert_return(callback, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -1064,7 +1105,7 @@ _public_ int sd_event_add_post(
         if (r < 0)
                 return r;
 
-        s = source_new(e, SOURCE_POST);
+        s = source_new(e, !ret, SOURCE_POST);
         if (!s)
                 return -ENOMEM;
 
@@ -1078,7 +1119,9 @@ _public_ int sd_event_add_post(
                 return r;
         }
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -1093,7 +1136,6 @@ _public_ int sd_event_add_exit(
 
         assert_return(e, -EINVAL);
         assert_return(callback, -EINVAL);
-        assert_return(ret, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -1103,7 +1145,7 @@ _public_ int sd_event_add_exit(
                         return -ENOMEM;
         }
 
-        s = source_new(e, SOURCE_EXIT);
+        s = source_new(e, !ret, SOURCE_EXIT);
         if (!s)
                 return -ENOMEM;
 
@@ -1118,7 +1160,9 @@ _public_ int sd_event_add_exit(
                 return r;
         }
 
-        *ret = s;
+        if (ret)
+                *ret = s;
+
         return 0;
 }
 
@@ -1151,6 +1195,8 @@ _public_ sd_event_source* sd_event_source_unref(sd_event_source *s) {
                 if (s->dispatching) {
                         if (s->type == SOURCE_IO)
                                 source_io_unregister(s);
+
+                        source_disconnect(s);
                 } else
                         source_free(s);
         }
@@ -1995,7 +2041,7 @@ static int source_dispatch(sd_event_source *s) {
                 break;
 
         case SOURCE_WATCHDOG:
-        case _SOUFCE_EVENT_SOURCE_TYPE_MAX:
+        case _SOURCE_EVENT_SOURCE_TYPE_MAX:
         case _SOURCE_EVENT_SOURCE_TYPE_INVALID:
                 assert_not_reached("Wut? I shouldn't exist.");
         }