[systemd-bugs] [Bug 84659] New: sd_event fails miserably with more than one child process

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=84659

            Bug ID: 84659
           Summary: sd_event fails miserably with more than one child
                    process
           Product: systemd
           Version: unspecified
          Hardware: Other
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: general
          Assignee: systemd-bugs at lists.freedesktop.org
          Reporter: mustrumr97 at gmail.com
        QA Contact: systemd-bugs at lists.freedesktop.org

When a child event is disabled (in order to be freed) and there is no SIGCHLD
signal event, sd_event_source_set_enabled will disable SIGCHLD even if there
are other child events.

My fix also removes some unneeded signalfd updates.

diff --git a/src/libsystemd/sd-event/sd-event.c
b/src/libsystemd/sd-event/sd-event.c
index b56182d..42b176b 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -1055,11 +1055,9 @@ _public_ int sd_event_add_child(
                 return r;
         }

-        e->n_enabled_child_sources ++;
-
         assert_se(sigaddset(&e->sigset, SIGCHLD) == 0);

-        if (!e->signal_sources || !e->signal_sources[SIGCHLD]) {
+        if ((!e->signal_sources || !e->signal_sources[SIGCHLD]) &&
e->n_enabled_child_sources == 0) {
                 r = event_update_signal_fd(e);
                 if (r < 0) {
                         source_free(s);
@@ -1067,6 +1065,8 @@ _public_ int sd_event_add_child(
                 }
         }

+        e->n_enabled_child_sources ++;
+
         e->need_process_child = true;

         if (ret)
@@ -1451,7 +1451,7 @@ _public_ int sd_event_source_set_enabled(sd_event_source
*s, int m) {
                         assert(s->event->n_enabled_child_sources > 0);
                         s->event->n_enabled_child_sources--;

-                        if (!s->event->signal_sources ||
!s->event->signal_sources[SIGCHLD]) {
+                        if ((!s->event->signal_sources ||
!s->event->signal_sources[SIGCHLD]) && s->event->n_enabled_child_sources == 0)
{
                                 assert_se(sigdelset(&s->event->sigset,
SIGCHLD) == 0);
                                 event_update_signal_fd(s->event);
                         }
@@ -1511,12 +1511,12 @@ _public_ int
sd_event_source_set_enabled(sd_event_source *s, int m) {

                 case SOURCE_CHILD:
                         if (s->enabled == SD_EVENT_OFF) {
-                                s->event->n_enabled_child_sources++;
-
-                                if (!s->event->signal_sources ||
!s->event->signal_sources[SIGCHLD]) {
+                                if ((!s->event->signal_sources ||
!s->event->signal_sources[SIGCHLD]) && s->event->n_enabled_child_sources == 0)
{
                                         assert_se(sigaddset(&s->event->sigset,
SIGCHLD) == 0);
                                         event_update_signal_fd(s->event);
                                 }
+
+                                s->event->n_enabled_child_sources++;
                         }

                         s->enabled = m;

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