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From a46d3732a4f8baacf1be3e5e0ac152119fe26d4c Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Renaud=20M=C3=A9trich?= <rmetrich@redhat.com>
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Date: Fri, 2 Oct 2020 17:30:35 +0200
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Subject: [PATCH] unit: don't emit PropertiesChanged signal if adding a
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 dependency to a unit is a no-op
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(cherry picked from commit 5177cb0a9add4ae568cff6e6f7c2b3c77760c343)
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Resolves: #1948480
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---
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 src/core/unit.c | 14 +++++++++++++-
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 1 file changed, 13 insertions(+), 1 deletion(-)
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diff --git a/src/core/unit.c b/src/core/unit.c
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index 68affa2c0e..e3e534ea2e 100644
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--- a/src/core/unit.c
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+++ b/src/core/unit.c
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@@ -2818,6 +2818,9 @@ int unit_add_dependency(
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         };
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         Unit *original_u = u, *original_other = other;
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         int r;
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+        /* Helper to know whether sending a notification is necessary or not:
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+         * if the dependency is already there, no need to notify! */
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+        bool noop = true;
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         assert(u);
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         assert(d >= 0 && d < _UNIT_DEPENDENCY_MAX);
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@@ -2842,24 +2845,33 @@ int unit_add_dependency(
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         r = unit_add_dependency_hashmap(u->dependencies + d, other, mask, 0);
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         if (r < 0)
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                 return r;
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+        else if (r > 0)
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+                noop = false;
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         if (inverse_table[d] != _UNIT_DEPENDENCY_INVALID && inverse_table[d] != d) {
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                 r = unit_add_dependency_hashmap(other->dependencies + inverse_table[d], u, 0, mask);
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                 if (r < 0)
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                         return r;
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+                else if (r > 0)
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+                        noop = false;
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         }
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         if (add_reference) {
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                 r = unit_add_dependency_hashmap(u->dependencies + UNIT_REFERENCES, other, mask, 0);
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                 if (r < 0)
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                         return r;
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+                else if (r > 0)
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+                        noop = false;
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                 r = unit_add_dependency_hashmap(other->dependencies + UNIT_REFERENCED_BY, u, 0, mask);
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                 if (r < 0)
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                         return r;
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+                else if (r > 0)
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+                        noop = false;
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         }
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-        unit_add_to_dbus_queue(u);
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+        if (!noop)
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+                unit_add_to_dbus_queue(u);
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         return 0;
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 }
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