[banshee] Dap: add locking around DapSync.library_syncs field (bgo#614039)

[Andrés Aragoneses <aaragoneses src gnome org>]

commit 14c02083d01ce82467361bafb4bfc902c8e9eaaf
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Wed Jul 8 01:24:34 2015 +0200

    Dap: add locking around DapSync.library_syncs field (bgo#614039)
    
    As the stacktrace in comment#3 of bug#614039 shows
    (https://bugzilla.gnome.org/show_bug.cgi?id=614039#c3)
    there may be more than one thread accessing this field,
    so we need locking around the code that modifies it and
    the code that iterates it.
    
    In regards to the Libraries property, as its public,
    we make it do a copy of the list before returning it
    to external consumers, but also locking while making
    the copy. Also, to prevent external consumers from
    modifying it (because they cannot hold the private
    lock), we make its type be IEnumerable instead of IList.
    
    This should prevent all data races around this field,
    and fixes the last part of bug bgo#614039.

 src/Dap/Banshee.Dap/Banshee.Dap/DapSync.cs         |   93 +++++++++++++-------
 .../Banshee.Podcasting.Gui/PodcastActions.cs       |    3 +-
 2 files changed, 62 insertions(+), 34 deletions(-)
---
diff --git a/src/Dap/Banshee.Dap/Banshee.Dap/DapSync.cs b/src/Dap/Banshee.Dap/Banshee.Dap/DapSync.cs
index d11ec90..55f6781 100644
--- a/src/Dap/Banshee.Dap/Banshee.Dap/DapSync.cs
+++ b/src/Dap/Banshee.Dap/Banshee.Dap/DapSync.cs
@@ -53,7 +53,10 @@ namespace Banshee.Dap
     {
         private DapSource dap;
         private string conf_ns;
+
         private List<DapLibrarySync> library_syncs = new List<DapLibrarySync> ();
+        private object library_syncs_mutex = new object ();
+
         internal SchemaEntry<bool> LegacyManuallyManage;
         private SchemaEntry<bool> auto_sync;
         private Section sync_prefs;
@@ -76,12 +79,20 @@ namespace Banshee.Dap
             get { return dap; }
         }
 
-        public IList<DapLibrarySync> Libraries {
-            get { return library_syncs; }
+        public IEnumerable<DapLibrarySync> Libraries {
+            get {
+                lock (library_syncs_mutex) {
+                    return library_syncs.ToArray ();
+                }
+            }
         }
 
         public bool Enabled {
-            get { return library_syncs.Any (l => l.Enabled); }
+            get {
+                lock (library_syncs_mutex) {
+                    return library_syncs.Any (l => l.Enabled);
+                }
+            }
         }
 
         public bool AutoSync {
@@ -105,10 +116,12 @@ namespace Banshee.Dap
 
         public void Dispose ()
         {
-            foreach (DapLibrarySync sync in library_syncs) {
-                sync.Library.TracksAdded -= OnLibraryChanged;
-                sync.Library.TracksDeleted -= OnLibraryChanged;
-                sync.Dispose ();
+            lock (library_syncs_mutex) {
+                foreach (DapLibrarySync sync in library_syncs) {
+                    sync.Library.TracksAdded -= OnLibraryChanged;
+                    sync.Library.TracksDeleted -= OnLibraryChanged;
+                    sync.Dispose ();
+                }
             }
 
             var src_mgr = ServiceManager.SourceManager;
@@ -173,7 +186,9 @@ namespace Banshee.Dap
             var library = GetSyncableLibrary (source);
             if (library != null) {
                 var sync = new DapLibrarySync (this, library);
-                library_syncs.Add (sync);
+                lock (library_syncs_mutex) {
+                    library_syncs.Add (sync);
+                }
                 library.TracksAdded += OnLibraryChanged;
                 library.TracksDeleted += OnLibraryChanged;
 
@@ -193,7 +208,10 @@ namespace Banshee.Dap
             var library = GetSyncableLibrary (source);
             if (library != null) {
 
-                var sync = library_syncs.FirstOrDefault (s => s.Library == library);
+                DapLibrarySync sync = null;
+                lock (library_syncs_mutex) {
+                    sync = library_syncs.FirstOrDefault (s => s.Library == library);
+                }
                 if (sync == null) {
                     return;
                 }
@@ -213,7 +231,9 @@ namespace Banshee.Dap
 
         private void SortLibraries ()
         {
-            library_syncs.Sort ((a, b) => a.Library.Order.CompareTo (b.Library.Order));
+            lock (library_syncs_mutex) {
+                library_syncs.Sort ((a, b) => a.Library.Order.CompareTo (b.Library.Order));
+            }
         }
 
         private void UpdateSensitivities ()
@@ -233,8 +253,10 @@ namespace Banshee.Dap
         private void OnDapChanged (Source sender, TrackEventArgs args)
         {
             if (!AutoSync && dap_loaded && !Syncing) {
-                foreach (DapLibrarySync lib_sync in library_syncs) {
-                    lib_sync.CalculateSync ();
+                lock (library_syncs_mutex) {
+                    foreach (DapLibrarySync lib_sync in library_syncs) {
+                        lib_sync.CalculateSync ();
+                    }
                 }
             }
         }
@@ -245,18 +267,19 @@ namespace Banshee.Dap
                 return;
             }
 
-            foreach (DapLibrarySync lib_sync in library_syncs) {
-                if (lib_sync.Library == sender) {
-                    if (AutoSync && lib_sync.Enabled) {
-                        Sync ();
-                    } else {
-                        lib_sync.CalculateSync ();
-                        OnUpdated ();
-                    }
-                    break;
+            DapLibrarySync lib_to_sync = null;
+            lock (library_syncs_mutex) {
+                lib_to_sync = library_syncs.FirstOrDefault (lib_sync => lib_sync.Library == sender);
+            }
+            if (lib_to_sync != null) {
+                if (AutoSync && lib_to_sync.Enabled) {
+                    Sync ();
+                } else {
+                    lib_to_sync.CalculateSync ();
+                    OnUpdated ();
                 }
             }
-         }
+        }
 
         private LibrarySource GetSyncableLibrary (Source source)
         {
@@ -294,8 +317,10 @@ namespace Banshee.Dap
 
         public void CalculateSync ()
         {
-            foreach (DapLibrarySync library_sync in library_syncs) {
-                library_sync.CalculateSync ();
+            lock (library_syncs_mutex) {
+                foreach (DapLibrarySync library_sync in library_syncs) {
+                    library_sync.CalculateSync ();
+                }
             }
 
             OnUpdated ();
@@ -321,9 +346,11 @@ namespace Banshee.Dap
         public override string ToString ()
         {
             System.Text.StringBuilder sb = new System.Text.StringBuilder ();
-            foreach (DapLibrarySync library_sync in library_syncs) {
-                sb.Append (library_sync.ToString ());
-                sb.Append ("\n");
+            lock (library_syncs_mutex) {
+                foreach (DapLibrarySync library_sync in library_syncs) {
+                    sb.Append (library_sync.ToString ());
+                    sb.Append ("\n");
+                }
             }
             return sb.ToString ();
         }
@@ -341,10 +368,12 @@ namespace Banshee.Dap
 
             bool sync_playlists = false;
             if (dap.SupportsPlaylists) {
-                foreach (DapLibrarySync library_sync in library_syncs) {
-                    if (library_sync.Library.SupportsPlaylists) {
-                        sync_playlists = true;
-                        break;
+                lock (library_syncs_mutex) {
+                    foreach (DapLibrarySync library_sync in library_syncs) {
+                        if (library_sync.Library.SupportsPlaylists) {
+                            sync_playlists = true;
+                            break;
+                        }
                     }
                 }
             }
@@ -353,7 +382,7 @@ namespace Banshee.Dap
                 dap.RemovePlaylists ();
             }
 
-            foreach (DapLibrarySync library_sync in library_syncs) {
+            foreach (DapLibrarySync library_sync in Libraries) {
                 try {
                     library_sync.Sync ();
                 } catch (DapLibrarySync.PossibleUserErrorException e) {
diff --git a/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Gui/PodcastActions.cs 
b/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Gui/PodcastActions.cs
index e6f28e5..f77f749 100644
--- a/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Gui/PodcastActions.cs
+++ b/src/Extensions/Banshee.Podcasting/Banshee.Podcasting.Gui/PodcastActions.cs
@@ -343,8 +343,7 @@ namespace Banshee.Podcasting.Gui
                 return;
             }
 
-            Uri tweaked_feed_uri;
-            if (!TryParseUrl (url, out feedUri) && !TryParseUrl ("http://"; + url, out tweaked_feed_uri)) {
+            if (!TryParseUrl (url, out feedUri)) {
                 HigMessageDialog.RunHigMessageDialog (
                     null,
                     DialogFlags.Modal,