From d7ad6ad123200f562081ff09f7bed3c6d969ac0a Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 23 Oct 2020 21:21:58 +0200
Subject: [PATCH] sd-event: split out enable and disable codepaths from
 sd_event_source_set_enabled()
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So far half of sd_event_source_set_enabled() was doing enabling, the
other half was doing disabling. Let's split that into two separate
calls.

(This also adds a new shortcut to sd_event_source_set_enabled(): if the
caller toggles between "ON" and "ONESHOT" we'll now shortcut this, since
the event source is already enabled in that case and shall remain
enabled.)

This heavily borrows and is inspired from Michal Sekletár's #17284
refactoring.

(cherry picked from commit ddfde737b546c17e54182028153aa7f7e78804e3)

Related: #1819868
---
 src/libsystemd/sd-event/sd-event.c | 227 +++++++++++++++--------------
 1 file changed, 121 insertions(+), 106 deletions(-)

diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index 47f99eb096..df5ed0dce8 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -2260,152 +2260,167 @@ _public_ int sd_event_source_get_enabled(sd_event_source *s, int *m) {
         return 0;
 }
 
-_public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
+static int event_source_disable(sd_event_source *s) {
         int r;
 
-        assert_return(s, -EINVAL);
-        assert_return(IN_SET(m, SD_EVENT_OFF, SD_EVENT_ON, SD_EVENT_ONESHOT), -EINVAL);
-        assert_return(!event_pid_changed(s->event), -ECHILD);
+        assert(s);
+        assert(s->enabled != SD_EVENT_OFF);
 
-        /* If we are dead anyway, we are fine with turning off
-         * sources, but everything else needs to fail. */
-        if (s->event->state == SD_EVENT_FINISHED)
-                return m == SD_EVENT_OFF ? 0 : -ESTALE;
+        /* Unset the pending flag when this event source is disabled */
+        if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
+                r = source_set_pending(s, false);
+                if (r < 0)
+                        return r;
+        }
 
-        if (s->enabled == m)
-                return 0;
+        s->enabled = SD_EVENT_OFF;
 
-        if (m == SD_EVENT_OFF) {
+        switch (s->type) {
 
-                /* Unset the pending flag when this event source is disabled */
-                if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
-                        r = source_set_pending(s, false);
-                        if (r < 0)
-                                return r;
-                }
+        case SOURCE_IO:
+                source_io_unregister(s);
+                break;
 
-                switch (s->type) {
+        case SOURCE_TIME_REALTIME:
+        case SOURCE_TIME_BOOTTIME:
+        case SOURCE_TIME_MONOTONIC:
+        case SOURCE_TIME_REALTIME_ALARM:
+        case SOURCE_TIME_BOOTTIME_ALARM:
+                event_source_time_prioq_reshuffle(s);
+                break;
 
-                case SOURCE_IO:
-                        source_io_unregister(s);
-                        s->enabled = m;
-                        break;
+        case SOURCE_SIGNAL:
+                event_gc_signal_data(s->event, &s->priority, s->signal.sig);
+                break;
 
-                case SOURCE_TIME_REALTIME:
-                case SOURCE_TIME_BOOTTIME:
-                case SOURCE_TIME_MONOTONIC:
-                case SOURCE_TIME_REALTIME_ALARM:
-                case SOURCE_TIME_BOOTTIME_ALARM:
-                        s->enabled = m;
-                        event_source_time_prioq_reshuffle(s);
-                        break;
+        case SOURCE_CHILD:
+                assert(s->event->n_enabled_child_sources > 0);
+                s->event->n_enabled_child_sources--;
 
-                case SOURCE_SIGNAL:
-                        s->enabled = m;
+                event_gc_signal_data(s->event, &s->priority, SIGCHLD);
+                break;
 
-                        event_gc_signal_data(s->event, &s->priority, s->signal.sig);
-                        break;
+        case SOURCE_EXIT:
+                prioq_reshuffle(s->event->exit, s, &s->exit.prioq_index);
+                break;
 
-                case SOURCE_CHILD:
-                        s->enabled = m;
+        case SOURCE_DEFER:
+        case SOURCE_POST:
+        case SOURCE_INOTIFY:
+                break;
 
-                        assert(s->event->n_enabled_child_sources > 0);
-                        s->event->n_enabled_child_sources--;
+        default:
+                assert_not_reached("Wut? I shouldn't exist.");
+        }
 
-                        event_gc_signal_data(s->event, &s->priority, SIGCHLD);
-                        break;
+        return 0;
+}
 
-                case SOURCE_EXIT:
-                        s->enabled = m;
-                        prioq_reshuffle(s->event->exit, s, &s->exit.prioq_index);
-                        break;
+static int event_source_enable(sd_event_source *s, int m) {
+        int r;
 
-                case SOURCE_DEFER:
-                case SOURCE_POST:
-                case SOURCE_INOTIFY:
-                        s->enabled = m;
-                        break;
+        assert(s);
+        assert(IN_SET(m, SD_EVENT_ON, SD_EVENT_ONESHOT));
+        assert(s->enabled == SD_EVENT_OFF);
 
-                default:
-                        assert_not_reached("Wut? I shouldn't exist.");
-                }
+        /* Unset the pending flag when this event source is enabled */
+        if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
+                r = source_set_pending(s, false);
+                if (r < 0)
+                        return r;
+        }
 
-        } else {
+        s->enabled = m;
 
-                /* Unset the pending flag when this event source is enabled */
-                if (s->enabled == SD_EVENT_OFF && !IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
-                        r = source_set_pending(s, false);
-                        if (r < 0)
-                                return r;
+        switch (s->type) {
+
+        case SOURCE_IO:
+                r = source_io_register(s, m, s->io.events);
+                if (r < 0) {
+                        s->enabled = SD_EVENT_OFF;
+                        return r;
                 }
 
-                switch (s->type) {
+                break;
 
-                case SOURCE_IO:
-                        r = source_io_register(s, m, s->io.events);
-                        if (r < 0)
-                                return r;
+        case SOURCE_TIME_REALTIME:
+        case SOURCE_TIME_BOOTTIME:
+        case SOURCE_TIME_MONOTONIC:
+        case SOURCE_TIME_REALTIME_ALARM:
+        case SOURCE_TIME_BOOTTIME_ALARM:
+                event_source_time_prioq_reshuffle(s);
+                break;
 
-                        s->enabled = m;
-                        break;
+        case SOURCE_SIGNAL:
+                r = event_make_signal_data(s->event, s->signal.sig, NULL);
+                if (r < 0) {
+                        s->enabled = SD_EVENT_OFF;
+                        event_gc_signal_data(s->event, &s->priority, s->signal.sig);
+                        return r;
+                }
 
-                case SOURCE_TIME_REALTIME:
-                case SOURCE_TIME_BOOTTIME:
-                case SOURCE_TIME_MONOTONIC:
-                case SOURCE_TIME_REALTIME_ALARM:
-                case SOURCE_TIME_BOOTTIME_ALARM:
-                        s->enabled = m;
-                        event_source_time_prioq_reshuffle(s);
-                        break;
+                break;
 
-                case SOURCE_SIGNAL:
+        case SOURCE_CHILD:
+                s->event->n_enabled_child_sources++;
 
-                        s->enabled = m;
+                r = event_make_signal_data(s->event, SIGCHLD, NULL);
+                if (r < 0) {
+                        s->enabled = SD_EVENT_OFF;
+                        s->event->n_enabled_child_sources--;
+                        event_gc_signal_data(s->event, &s->priority, SIGCHLD);
+                        return r;
+                }
 
-                        r = event_make_signal_data(s->event, s->signal.sig, NULL);
-                        if (r < 0) {
-                                s->enabled = SD_EVENT_OFF;
-                                event_gc_signal_data(s->event, &s->priority, s->signal.sig);
-                                return r;
-                        }
 
-                        break;
+                break;
 
-                case SOURCE_CHILD:
+        case SOURCE_EXIT:
+                prioq_reshuffle(s->event->exit, s, &s->exit.prioq_index);
+                break;
 
-                        if (s->enabled == SD_EVENT_OFF)
-                                s->event->n_enabled_child_sources++;
+        case SOURCE_DEFER:
+        case SOURCE_POST:
+        case SOURCE_INOTIFY:
+                break;
 
-                        s->enabled = m;
+        default:
+                assert_not_reached("Wut? I shouldn't exist.");
+        }
 
-                        r = event_make_signal_data(s->event, SIGCHLD, NULL);
-                        if (r < 0) {
-                                s->enabled = SD_EVENT_OFF;
-                                s->event->n_enabled_child_sources--;
-                                event_gc_signal_data(s->event, &s->priority, SIGCHLD);
-                                return r;
-                        }
+        return 0;
+}
 
-                        break;
+_public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
+        int r;
 
-                case SOURCE_EXIT:
-                        s->enabled = m;
-                        prioq_reshuffle(s->event->exit, s, &s->exit.prioq_index);
-                        break;
+        assert_return(s, -EINVAL);
+        assert_return(IN_SET(m, SD_EVENT_OFF, SD_EVENT_ON, SD_EVENT_ONESHOT), -EINVAL);
+        assert_return(!event_pid_changed(s->event), -ECHILD);
 
-                case SOURCE_DEFER:
-                case SOURCE_POST:
-                case SOURCE_INOTIFY:
-                        s->enabled = m;
-                        break;
+        /* If we are dead anyway, we are fine with turning off sources, but everything else needs to fail. */
+        if (s->event->state == SD_EVENT_FINISHED)
+                return m == SD_EVENT_OFF ? 0 : -ESTALE;
 
-                default:
-                        assert_not_reached("Wut? I shouldn't exist.");
+        if (s->enabled == m) /* No change? */
+                return 0;
+
+        if (m == SD_EVENT_OFF)
+                r = event_source_disable(s);
+        else {
+                if (s->enabled != SD_EVENT_OFF) {
+                        /* Switching from "on" to "oneshot" or back? If that's the case, we can take a shortcut, the
+                         * event source is already enabled after all. */
+                        s->enabled = m;
+                        return 0;
                 }
+
+                r = event_source_enable(s, m);
         }
+        if (r < 0)
+                return r;
 
         event_source_pp_prioq_reshuffle(s);
-
         return 0;
 }