From d26e8979891d549214c955104529177576cd9de0 Mon Sep 17 00:00:00 2001
From: Colin Walters <walters@verbum.org>
Date: Fri, 31 Mar 2017 16:19:58 -0400
Subject: [PATCH 1/2] main: Create a helper function for "owner wakeup"
 optimization

The original patch really should have introduced a helper - among
other things it deserves a code comment.  We're likely to make
further changes too, so it's obviously better to only do it in one
place.

See: https://bugzilla.gnome.org/show_bug.cgi?id=761102
---
 glib/gmain.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/glib/gmain.c b/glib/gmain.c
index 4f90574..88b57fd 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -1118,6 +1118,19 @@ source_remove_from_context (GSource      *source,
     }
 }
 
+/* See https://bugzilla.gnome.org/show_bug.cgi?id=761102 for
+ * the introduction of this.
+ *
+ * The main optimization is to avoid waking up the main
+ * context if a change is made by the current owner.
+ */
+static void
+conditional_wakeup (GMainContext *context)
+{
+  if (context->owner && context->owner != G_THREAD_SELF)
+    g_wakeup_signal (context->wakeup);
+}
+
 static guint
 g_source_attach_unlocked (GSource      *source,
                           GMainContext *context,
@@ -1164,8 +1177,8 @@ g_source_attach_unlocked (GSource      *source,
   /* If another thread has acquired the context, wake it up since it
    * might be in poll() right now.
    */
-  if (do_wakeup && context->owner && context->owner != G_THREAD_SELF)
-    g_wakeup_signal (context->wakeup);
+  if (do_wakeup)
+    conditional_wakeup (context);
 
   return source->source_id;
 }
@@ -1839,8 +1852,7 @@ g_source_set_ready_time (GSource *source,
     {
       /* Quite likely that we need to change the timeout on the poll */
       if (!SOURCE_BLOCKED (source))
-        if (context->owner && context->owner != G_THREAD_SELF)
-          g_wakeup_signal (context->wakeup);
+        conditional_wakeup (context);
       UNLOCK_CONTEXT (context);
     }
 }
@@ -4352,8 +4364,7 @@ g_main_context_add_poll_unlocked (GMainContext *context,
   context->poll_changed = TRUE;
 
   /* Now wake up the main loop if it is waiting in the poll() */
-  if (context->owner && context->owner != G_THREAD_SELF)
-    g_wakeup_signal (context->wakeup);
+  conditional_wakeup (context);
 }
 
 /**
@@ -4411,10 +4422,9 @@ g_main_context_remove_poll_unlocked (GMainContext *context,
     }
 
   context->poll_changed = TRUE;
-  
+
   /* Now wake up the main loop if it is waiting in the poll() */
-  if (context->owner && context->owner != G_THREAD_SELF)
-    g_wakeup_signal (context->wakeup);
+  conditional_wakeup (context);
 }
 
 /**
-- 
2.9.3


From c4b3fd1487dad9dece67453cef4954b07dd3bdc1 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <bonzini@gnu.org>
Date: Mon, 3 Apr 2017 13:32:32 -0400
Subject: [PATCH 2/2] gmain: Signal wakeups if context has never been acquired
 as well

Should address backwards compatibility with how qemu is using
`GMainContext`.

See https://bugzilla.gnome.org/show_bug.cgi?id=761102#c14

Input-into-keyboard-by: Colin Walters <walters@verbum.org>
---
 glib/gmain.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/glib/gmain.c b/glib/gmain.c
index 88b57fd..f390c46 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -1127,7 +1127,17 @@ source_remove_from_context (GSource      *source,
 static void
 conditional_wakeup (GMainContext *context)
 {
-  if (context->owner && context->owner != G_THREAD_SELF)
+  /* We want to signal wakeups in two cases:
+   *  1 When the context is owned by another thread
+   *  2 When the context owner is NULL (two subcases)
+   *   2a Possible if the context has never been acquired
+   *   2b Or if the context has no current owner
+   *
+   * At least case 2a) is necessary to ensure backwards compatibility with
+   * qemu's use of GMainContext.
+   * https://bugzilla.gnome.org/show_bug.cgi?id=761102#c14
+   */
+  if (context->owner != G_THREAD_SELF)
     g_wakeup_signal (context->wakeup);
 }
 
-- 
2.9.3