[evolution-data-server/gnome-3-18] [POP3] Avoid deadlock around pop3_folder_get_message_sync()

[Milan Crha <mcrha src gnome org>]

commit 50ce9f5828ca14e22a54e2f56b240b2fcd25a682
Author: Milan Crha <mcrha redhat com>
Date:   Thu Nov 26 15:16:26 2015 +0100

    [POP3] Avoid deadlock around pop3_folder_get_message_sync()
    
    The function could be called from within camel_pop3_folder_delete_old(),
    which already holds the lock, thus the later attempt leads to a deadlock.
    Reported by cooly.

 camel/providers/pop3/camel-pop3-folder.c |   30 +++++++++++++++++++++---------
 1 files changed, 21 insertions(+), 9 deletions(-)
---
diff --git a/camel/providers/pop3/camel-pop3-folder.c b/camel/providers/pop3/camel-pop3-folder.c
index f0f4b76..e41584f 100644
--- a/camel/providers/pop3/camel-pop3-folder.c
+++ b/camel/providers/pop3/camel-pop3-folder.c
@@ -395,10 +395,11 @@ pop3_folder_set_message_flags (CamelFolder *folder,
 }
 
 static CamelMimeMessage *
-pop3_folder_get_message_sync (CamelFolder *folder,
-                              const gchar *uid,
-                              GCancellable *cancellable,
-                              GError **error)
+pop3_folder_get_message_internal_sync (CamelFolder *folder,
+                                      const gchar *uid,
+                                      gboolean already_locked,
+                                      GCancellable *cancellable,
+                                      GError **error)
 {
        CamelStore *parent_store;
        CamelMimeMessage *message = NULL;
@@ -457,7 +458,7 @@ pop3_folder_get_message_sync (CamelFolder *folder,
 
        pop3_engine = camel_pop3_store_ref_engine (pop3_store);
 
-       if (!camel_pop3_engine_busy_lock (pop3_engine, cancellable, error))
+       if (!already_locked && !camel_pop3_engine_busy_lock (pop3_engine, cancellable, error))
                goto fail;
 
        /* If we have an oustanding retrieve message running, wait for that to complete
@@ -475,7 +476,8 @@ pop3_folder_get_message_sync (CamelFolder *folder,
                if (i == -1) {
                        g_prefix_error (
                                error, _("Cannot get message %s: "), uid);
-                       camel_pop3_engine_busy_unlock (pop3_engine);
+                       if (!already_locked)
+                               camel_pop3_engine_busy_unlock (pop3_engine);
                        goto fail;
                }
        }
@@ -586,7 +588,8 @@ pop3_folder_get_message_sync (CamelFolder *folder,
                camel_medium_add_header (CAMEL_MEDIUM (message), "X-Evolution-POP3-UID", uid);
        }
 done:
-       camel_pop3_engine_busy_unlock (pop3_engine);
+       if (!already_locked)
+               camel_pop3_engine_busy_unlock (pop3_engine);
        g_clear_object (&stream);
 fail:
        g_clear_object (&pop3_engine);
@@ -596,6 +599,15 @@ fail:
        return message;
 }
 
+static CamelMimeMessage *
+pop3_folder_get_message_sync (CamelFolder *folder,
+                              const gchar *uid,
+                              GCancellable *cancellable,
+                              GError **error)
+{
+       return pop3_folder_get_message_internal_sync (folder, uid, FALSE, cancellable, error);
+}
+
 static gboolean
 pop3_folder_refresh_info_sync (CamelFolder *folder,
                                GCancellable *cancellable,
@@ -1079,8 +1091,8 @@ camel_pop3_folder_delete_old (CamelFolder *folder,
                d (printf ("%s(%d): fi->uid=[%s]\n", __FILE__, __LINE__, fi->uid));
                if (!pop3_get_message_time_from_cache (folder, fi->uid, &message_time)) {
                        d (printf ("could not get message time from cache, trying from pop3\n"));
-                       message = pop3_folder_get_message_sync (
-                               folder, fi->uid, cancellable, error);
+                       message = pop3_folder_get_message_internal_sync (
+                               folder, fi->uid, TRUE, cancellable, error);
                        if (message) {
                                message_time = message->date + message->date_offset;
                                g_object_unref (message);